ORCID Profile
0000-0001-9140-6724
Current Organisation
Linköpings universitet
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Publisher: Springer Science and Business Media LLC
Date: 05-2018
Publisher: AIP Publishing
Date: 2020
DOI: 10.1063/1.5134862
Abstract: We study the origin of layer decoupling in ordered multilayer graphene grown by high temperature sublimation on C-face 4H-SiC. The mid-infrared optical Hall effect technique is used to determine the magnetic field dependence of the inter-Landau level transition energies and their optical polarization selection rules, which unambiguously show that the multilayer graphene consists of electronically decoupled layers. Transmission electron microscopy reveals no out-of-plane rotational disorder between layers in the stack, which is in contrast to what is typically observed for C-face graphene grown by low temperature sublimation. It is found that the multilayer graphene maintains AB-stacking order with increased interlayer spacing by 2.4%–8.4% as compared to highly oriented pyrolytic graphite. Electron energy loss spectroscopy mapping reveals Si atoms trapped in between layers, which are proposed to be the cause for the observed increased interlayer spacing leading to layer decoupling. Based on our results, we propose a defect-driven growth evolution mechanism for multilayer graphene on C-face SiC via high temperature sublimation.
Publisher: Elsevier BV
Date: 2010
Publisher: AIP Publishing
Date: 24-09-2001
DOI: 10.1063/1.1402160
Abstract: Heavily Al-doped 4H–SiC structures have been prepared by vapor phase epitaxy. Subsequent anneals have been carried out in an Ar atmosphere in a rf-heated furnace between 1500 °C and 2000 °C for 0.5 to 3 h. Secondary ion mass spectrometry has been utilized to obtain Al concentration versus depth as well as lateral distributions (ion images). Transmission electron microscopy (TEM) has been employed to study the crystallinity and determine phase composition after heat treatment. A solubility limit of ∼2×1020 Al/cm3 (1900 °C) is extracted. Three-dimensional ion images show that the Al distribution does not remain homogeneous in layers heat treated at 1700 °C or above when the Al concentration exceeds 2×1020 cm−3. Al-containing precipitates are identified by energy-filtered TEM.
Publisher: American Physical Society (APS)
Date: 02-06-2010
Publisher: MDPI AG
Date: 13-10-2020
DOI: 10.3390/AGRICULTURE10100470
Abstract: Photoperiod, vernalization, and plant height controlling genes are major developmental genes in wheat that govern environmental adaptation and hence, knowledge on the interaction effects among different alleles of these genes is crucial in breeding cultivars for target environments. The interaction effects among these genes were studied in nineteen Australian advanced lines from erse germplasm pools and four commercial checks. Diagnostic markers for the Vrn-A1 locus revealed the presence of the spring allele Vrn-A1a in 10 lines and Vrn-A1c in one line. The dominant alleles of Vrn-B1a and Vrn-D1a were identified in 19 and 8 lines, respectively. The most common photoperiod-insensitive allele of Ppd-D1a was identified in 19 lines and three and four copy photoperiod-insensitive alleles (Ppd-B1a and Ppd-B1c) were present in five and one lines, respectively. All the lines were photoperiod-sensitive for the Ppd-A1 locus. All lines were semi-dwarf, having either of the two dwarfing alleles 14 lines had the Rht-B1b (Rht-1) and the remaining had the Rht-D1b (Rht-2) dwarfing allele. The presence of the photoperiod-insensitive allele Ppd-D1a along with one or two spring alleles at the Vrn1 loci resulted in an earlier heading and better yield. Dwarfing genes were found to modify the heading time—the Rht-D1b allele advanced heading by three days and also showed superior effects on yield-contributing traits, indicating its beneficial role in yield under rain-fed conditions along with an appropriate combination of photoperiod and vernalization alleles. This study also identified the adaptability value of these allelic combinations for higher grain yield and protein content across the different the water-limited environments.
Publisher: MDPI AG
Date: 23-07-2020
Abstract: Selective-area grown, catalyst-free GaN nanorod (NR) arrays grown on Si substrates have been realized using liquid-target reactive magnetron sputter epitaxy (MSE). Focused ion beam lithography (FIBL) was applied to pattern Si substrates with TiNx masks. A liquid Ga target was sputtered in a mixture gas of Ar and N2, ranging the N2 partial pressure (PN₂) ratio from 100% to 50%. The growth of NRs shows a strong correlation with PN₂ on the selectivity, coalescence, and growth rate of NRs in both radial and axial directions. The growth rate of NRs formed inside the nanoholes increases monotonically with PN₂. The PN₂ ratio between 80% and 90% was found to render both a high growth rate and high selectivity. When the PN₂ ratio was below 80%, multiple NRs were formed in the nanoholes. For a PN₂ ratio higher than 90%, parasitic NRs were grown on the mask. An observed dependence of growth behavior upon the PN₂ ratio is attributed to a change in the effective Ga/N ratio on the substrate surface, as an effect of impinging reactive species, surface diffusivity, and residence time of adatoms. The mechanism of NR growth control was further investigated by studying the effect of nanoholes array pitch and growth temperature. The surface diffusion and the direct impingement of adatoms were found to be the dominant factors affecting the lateral and axial growth rates of NR, respectively, which were well elucidated by the collection area model.
Publisher: IOP Publishing
Date: 25-01-2022
Abstract: The impact on the performance of GaN high electron mobility transistors (HEMTs) of in situ ammonia (NH 3 ) pre-treatment prior to the deposition of silicon nitride (SiN) passivation with low-pressure chemical vapor deposition (LPCVD ) is investigated. Three different NH 3 pre-treatment durations (0, 3, and 10 min) were compared in terms of interface properties and device performance. A reduction of oxygen (O) at the interface between SiN and epi-structure is detected by scanning transmission electron microscopy (STEM )-electron energy loss spectroscopy (EELS) measurements in the s le subjected to 10 min of pre-treatment. The s les subjected to NH 3 pre-treatment show a reduced surface-related current dispersion of 9% (compared to 16% for the untreated s le), which is attributed to the reduction of O at the SiN/epi interface. Furthermore, NH 3 pre-treatment for 10 min significantly improves the current dispersion uniformity from 14.5% to 1.9%. The reduced trapping effects result in a high output power of 3.4 W mm −1 at 3 GHz (compared to 2.6 W mm −1 for the untreated s le). These results demonstrate that the in situ NH 3 pre-treatment before LPCVD of SiN passivation is critical and can effectively improves the large-signal microwave performance of GaN HEMTs.
Publisher: AIP Publishing
Date: 22-07-2002
DOI: 10.1063/1.1494865
Abstract: We report on the synthesis and characterization of epitaxial single-crystalline Ti3SiC2 films (Mn+1AXn-phase). Two original deposition techniques are described, (i) magnetron sputtering from Ti3SiC2 compound target and (ii) sputtering from in idual titanium and silicon targets with co-evaporated C60 as carbon source. Epitaxial Ti3SiC2 films of single-crystal quality were grown at 900 °C with both techniques. Epitaxial TiC(111) deposited in situ on MgO(111) by Ti sputtering using C60 as carbon source was used to nucleate the Ti3SiC2 films. The epitaxial relationship was found to be Ti3SiC2(0001)//TiC(111)//MgO(111) with the in-plane orientation Ti3SiC2[100]//TiC[101]//MgO[101].
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9RA10007E
Abstract: Reduction of thermal conductivity of sputtered CaMn 1−x Nb x O 3 thin films by secondary Ruddlesden–Popper phase and grain size optimization.
Publisher: American Chemical Society (ACS)
Date: 02-12-2209
Publisher: AIP Publishing
Date: 19-05-2003
DOI: 10.1063/1.1569027
Abstract: 4H–SiC epilayers were implanted with Al27 in doses from 1.3×1014 cm−2 to 7.8×1014 cm−2. Dislocation loop formation after high-temperature annealing was studied by plan-view transmission electron microscopy and high-resolution cross-sectional transmission electron microscopy. The total dislocation loop area was found to vary linearly with the implanted dose. For each dose, the total dislocation loop area, reflecting the amount of interstitials bound to loops, stays constant both with prolonged annealing and increasing temperature. Simultaneously, the average radius of the dislocation loops increases, indicating a process similar to Ostwald ripening.
Publisher: Elsevier BV
Date: 05-2006
Publisher: American Chemical Society (ACS)
Date: 30-05-2018
Publisher: Springer Science and Business Media LLC
Date: 18-01-2021
Publisher: Elsevier BV
Date: 09-2016
Publisher: Elsevier BV
Date: 2018
Publisher: Elsevier BV
Date: 2017
Publisher: American Chemical Society (ACS)
Date: 07-12-2020
Publisher: Wiley
Date: 20-05-2022
Abstract: Here, a new family of 2D transition metal carbo‐chalcogenides (TMCCs) is reported, which can be considered a combination of two well‐known families, TM carbides (MXenes) and TM dichalcogenides (TMDCs), at the atomic level. Single sheets are successfully obtained from multilayered Nb 2 S 2 C and Ta 2 S 2 C using electrochemical lithiation followed by sonication in water. The parent multilayered TMCCs are synthesized using a simple, scalable solid‐state synthesis followed by a topochemical reaction. Superconductivity transition is observed at 7.55 K for Nb 2 S 2 C. The delaminated Nb 2 S 2 C outperforms both multilayered Nb 2 S 2 C and delaminated NbS 2 as an electrode material for Li‐ion batteries. Ab initio calculations predict the elastic constant of TMCC to be over 50% higher than that of TMDC.
Publisher: Elsevier BV
Date: 07-2003
Publisher: Frontiers Media SA
Date: 14-07-2020
Publisher: AIP Publishing
Date: 16-09-2013
DOI: 10.1063/1.4820581
Abstract: Using in situ high-temperature (1073–1173 K) transmission electron microscopy, we investigated the thermal stability of Pt and Mo in contact with polycrystalline ZrB2 thin films deposited on Al2O3(0001). During annealing, we observed the diffusion of cubic-structured Pt1−xMox (with x = 0.2 ± 0.1) along the length of the ZrB2 layer. From the time-dependent increase in diffusion lengths, we determined that the Pt1−xMox does not react with ZrB2, but diffuses along the surface with a constant temperature-dependent velocity. We identify the rate-limiting step controlling the observed phenomenon as the flux of Mo atoms with an associated activation barrier of 3.8 ± 0.5 eV.
Publisher: Springer Science and Business Media LLC
Date: 17-07-2020
Publisher: Springer Science and Business Media LLC
Date: 14-03-2017
DOI: 10.1038/SREP44390
Abstract: The spinodal decomposition and thermal stability of thin In 0.72 Al 0.28 N layers and In 0.72 Al 0.28 N/AlN superlattices with AlN(0001) templates on Al 2 O 3 (0001) substrates was investigated by in-situ heating up to 900 °C. The thermally activated structural and chemical evolution was investigated in both plan-view and cross-sectional geometries by scanning transmission electron microscopy in combination with valence electron energy loss spectroscopy. The plan-view observations demonstrate evidence for spinodal decomposition of metastable In 0.72 Al 0.28 N after heating at 600 °C for 1 h. During heating compositional modulations in the range of 2–3 nm-size domains are formed, which coarsen with applied thermal budgets. Cross-sectional observations reveal that spinodal decomposition begin at interfaces and column boundaries, indicating that the spinodal decomposition has a surface-directed component.
Publisher: Institute of Physics, Polish Academy of Sciences
Date: 08-2007
Publisher: Wiley
Date: 10-10-2011
Abstract: Epitaxial growth of sp 2 ‐hybridized boron nitride (BN) using chemical vapour deposition, with ammonia and triethyl boron as precursors, is enabled on sapphire by introducing an aluminium nitride (AlN) buffer layer. This buffer layer is formed by initial nitridation of the substrate. Epitaxial growth is verified by X‐ray diffraction measurements in Bragg–Brentano configuration, pole figure measurements and transmission electron microscopy. The in‐plane stretching vibration of sp 2 ‐hybridized BN is observed at 1366 cm –1 from Raman spectroscopy. Time‐of‐flight elastic recoil detection analysis confirms almost perfect stoichiometric BN with low concentration of carbon, oxygen and hydrogen contaminations. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Publisher: Elsevier BV
Date: 04-2022
Publisher: American Chemical Society (ACS)
Date: 26-02-2021
Publisher: Shanghai Institute of Ceramics
Date: 2019
DOI: 10.15541/JIM20180377
Publisher: Optica Publishing Group
Date: 2006
DOI: 10.1364/AO.45.000137
Abstract: Cr-Ti multilayers with ultrashort periods of 1.39-2.04 nm have been grown for the first time as highly reflective, soft-x-ray multilayer, near-normal incidence mirrors for transition radiation and Cherenkov radiation x-ray sources based on the Ti-2p absorption edge at E = 452 eV (lambda = 2.74 nm). Hard, as well as soft, x-ay reflectivity and transmission electron microscopy were used to characterize the nanostructure of the mirrors. To achieve minimal accumulated roughness, improved interface flatness, and to avoid intermixing at the interfaces, each in idual layer was engineered by use of a two-stage ion assistance process during magnetron sputter deposition: The first 0.3 nm of each Ti and Cr layer was grown without ion assistance, and the remaining 0.39-0.72 nm of the layers were grown with high ion-neutral flux ratios phi (phiTi = 3.3, phiCr = 2.2) and a low energy Eion (ETi = 23.7 and ECr = 21.2), ion assistance. A maximum soft-x-ray reflectivity of R = 2.1% at near-normal incidence (approximately 78.8 degrees) was achieved for a multilayer mirror containing 100 bilayers with a modulation period of 1.379 nm and a layer thickness ratio of tau = 0.5. For a polarizing multilayer mirror with 150 bilayers designed for operation at the Brewster angle, 45 degrees, an extinction ratio, Rs/Rp, of 266 was achieved with an absolute reflectivity of R = 4.3%.
Publisher: AIP Publishing
Date: 16-08-2002
DOI: 10.1063/1.1499749
Abstract: Transmission electron microscopy was used to investigate B11, C12, N14, Al27, Si28, and Ar37 ion-implanted 4H-SiC epilayers and subsequent defect formation after high temperature annealing. During the annealing process extrinsic dislocation loops of interstitial type are formed on the SiC basal plane with a depth distribution roughly corresponding to the distribution of the implanted ions. The investigation reveals that in s les where the implanted ions are substituting for a position in the silicon sublattice, generating an excess of interstitial silicon, the dislocation loops are more readily formed than in a s le implanted with an ion substituting for carbon.
Publisher: Elsevier BV
Date: 11-2022
Publisher: No publisher found
Date: 2004
DOI: 10.1063/1.1790571
Publisher: Wiley
Date: 19-12-2002
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 02-2011
Publisher: Wiley
Date: 12-01-2022
Abstract: CaMnO 3 is a perovskite with attractive magnetic and thermoelectric properties. CaMnO 3 films are usually grown by pulsed laser deposition or radio frequency magnetron sputtering from ceramic targets. Herein, epitaxial growth of CaMnO 3– y (002) films on a ‐oriented LaAlO 3 substrate using pulsed direct current reactive magnetron sputtering is demonstrated, which is more suitable for industrial scale depositions. The CaMnO 3– y shows growth with a small in‐plane tilt of ≈0.2° toward the (200) plane of CaMnO 3– y and the () with respect to the LaAlO 3 substrate. X‐ray photoelectron spectroscopy of the electronic core levels shows an oxygen deficiency described by CaMnO 2.58 that yields a lower Seebeck coefficient and a higher electrical resistivity when compared to stoichiometric CaMnO 3 . The LaAlO 3 substrate promotes tensile‐strained growth of single crystals. Scanning transmission electron microscopy and electron energy loss spectroscopy reveal antiphase boundaries composed of Ca on Mn sites along and , forming stacking faults.
Publisher: AIP Publishing
Date: 09-2006
DOI: 10.1063/1.2338142
Abstract: The annealing behavior of interstitial-type basal plane dislocation loops in Al ion implanted 4H-SiC is investigated. It is shown that the loops undergo a dynamical ripening process. For annealing below 1700°C the total area of dislocation loops increases, indicating that point defects are still available for accumulation, but for annealing times longer than 100min at this temperature the value of the total loop area saturates. For longer annealing times, or higher temperatures, the dislocation loops are subjected to a conservative coarsening process, also known as Ostwald ripening. In this process the mean loop radius increases with increasing annealing time and temperature while the number of loops decreases. Meanwhile the summarized area of the loops stays constant. The observed ripening is suggested to occur by a mechanism, which involves coarsening by direct loop coalescence. Through this mechanism, loops on the same basal plane move towards each other until they coalesce into one, but loops on neighboring basal planes can only move until their loop edges meet (in a basal plane projection) where they remain. Climb along the c axis is not favorable as shown by experimental results and is suggested to be caused by the atomic configuration of the loop. Upon continuous annealing, this results in a situation where the loops are confined in clusters.
Publisher: Springer Science and Business Media LLC
Date: 30-12-2016
Publisher: American Vacuum Society
Date: 28-04-2016
DOI: 10.1116/1.4948234
Abstract: DC magnetron sputtering was used to deposit molybdenum boride thin films for potential low-friction applications. The films exhibit a nanocomposite structure with ∼10 nm large MoB2−x (x & 0.4) grains surrounded by a boron-rich tissue phase. The preferred formation of the metastable and substoichiometric hP3-MoB2 structure (AlB2-type) is explained with kinetic constraints to form the thermodynamically stable hR18-MoB2 phase with a very complex crystal structure. Nanoindentation revealed a relatively high hardness of (29 ± 2) GPa, which is higher than bulk s les. The high hardness can be explained by a hardening effect associated with the nanocomposite microstructure where the surrounding tissue phase restricts dislocation movement. A tribological study confirmed a significant formation of a tribofilm consisting of molybdenum oxide and boron oxide, however, without any lubricating effects at room temperature.
Publisher: Elsevier BV
Date: 08-2022
Publisher: American Physical Society (APS)
Date: 07-12-2011
Publisher: American Chemical Society (ACS)
Date: 03-12-2019
Abstract: Liquid-phase exfoliation of zirconium trisulfide (ZrS
Publisher: American Chemical Society (ACS)
Date: 04-02-2019
Abstract: Two-dimensional (2D) materials have attracted intense attention in nanoscience and nanotechnology due to their outstanding properties. Among these materials, the emerging family of 2D transition metal carbides, carbonitrides, and nitrides (referred to as MXenes) stands out because of the vast available chemical space for tuning materials chemistry and surface termination, offering opportunities for property tailoring. Specifically, semiconducting properties are needed to enable utilization in optoelectronics, but direct band gaps are experimentally challenging to achieve in these 2D carbides. Here, we demonstrate the fabrication of 2D hydroxyl-functionalized and carbon-deficient scandium carbide, namely, ScC
Publisher: IOP Publishing
Date: 06-05-2015
DOI: 10.1088/0957-4484/26/21/215602
Abstract: Catalystless growth of InxAl(1-x)N core-shell nanorods have been realized by reactive magnetron sputter epitaxy onto Si(111) substrates. The s les were characterized by scanning electron microscopy, x-ray diffraction, scanning transmission electron microscopy, and energy dispersive x-ray spectroscopy. The composition and morphology of InxAl(1-x)N nanorods are found to be strongly influenced by the growth temperature. At lower temperatures, the grown materials form well-separated and uniform core-shell nanorods with high In-content cores, while a deposition at higher temperature leads to the formation of an Al-rich InxAl(1-x)N film with vertical domains of low In-content as a result of merging Al-rich shells. The thickness and In content of the cores (domains) increase with decreasing growth temperature. The growth of the InxAl(1-x)N is traced to the initial stage, showing that the formation of the core-shell nanostructures starts very close to the interface. Phase separation due to spinodal decomposition is suggested as the origin of the resultant structures. Moreover, the in-plane crystallographic relationship of the nanorods and substrate was modified from a fiber textured to an epitaxial growth with an epitaxial relationship of InxAl(1-x)N[0001]//Si[111] and InxAl(1-x)N[1120]//Si[110 by removing the native SiOx layer from the substrate.
Publisher: AIP Publishing
Date: 11-02-2008
DOI: 10.1063/1.2838456
Abstract: Thin films of Ti2AlC MAX phase have been deposited using a multiple cathode pulsed cathodic arc. Evidence for substantial oxygen incorporation in the MAX phase is presented, likely originating from residual gas present in the vacuum chamber during deposition. The characteristic MAX phase crystal structure is maintained, in agreement with ab initio calculations, supporting substitutional O in C lattice positions. On the basis of these results, we propose the existence of a MAX phase-like material with material properties tuned by the incorporation of oxygen. Additionally, possible unintentional O incorporation in previously reported MAX phase materials is suggested.
Publisher: Springer Science and Business Media LLC
Date: 26-07-2005
Publisher: American Chemical Society (ACS)
Date: 22-07-2019
Abstract: A Ti
Publisher: AIP Publishing
Date: 2011
DOI: 10.1063/1.3527960
Abstract: The Mn+1AXn (MAX) phases are ternary compounds comprising alternating layers of a transition metal carbide or nitride and a third “A-group” element. The effect of substrate orientation on the growth of Ti2AlC MAX phase films was investigated by studying pulsed cathodic arc deposited s les grown on sapphire cut along the (0001), (101¯0), and (11¯02) crystallographic planes. Characterization of these s les was by x-ray diffraction, atomic force microscopy, and cross-sectional transmission electron microscopy. On the (101¯0) substrate, tilted (101¯8) growth of Ti2AlC was found, such that the TiC octahedra of the MAX phase structure have the same orientation as a spontaneously formed epitaxial TiC sublayer, preserving the typical TiC–Ti2AlC epitaxial relationship and confirming the importance of this relationship in determining MAX phase film orientation. An additional component of Ti2AlC with tilted fiber texture was observed in this s le tilted fiber texture, or axiotaxy, has not previously been seen in MAX phase films.
Publisher: Elsevier BV
Date: 06-2021
Publisher: Wiley
Date: 05-08-2021
Abstract: Exploratory theoretical predictions in uncharted structural and compositional space are integral to materials discoveries. Inspired by M 5 SiB 2 (T2) phases, the finding of a family of laminated quaternary metal borides, M ′ 4 M ″SiB 2 , with out‐of‐plane chemical order is reported here. 11 chemically ordered phases as well as 40 solid solutions, introducing four elements previously not observed in these borides are predicted. The predictions are experimentally verified for Ti 4 MoSiB 2 , establishing Ti as part of the T2 boride compositional space. Chemical exfoliation of Ti 4 MoSiB 2 and select removal of Si and MoB 2 sub‐layers is validated by derivation of a 2D material, TiO x Cl y , of high yield and in the form of delaminated sheets. These sheets have an experimentally determined direct band gap of ≈4.1 eV, and display characteristics suitable for supercapacitor applications. The results take the concept of chemical exfoliation beyond currently available 2D materials, and expands the envelope of 3D and 2D candidates, and their applications.
Publisher: Springer Science and Business Media LLC
Date: 25-04-2017
DOI: 10.1038/NCOMMS14949
Abstract: The exploration of two-dimensional solids is an active area of materials discovery. Research in this area has given us structures spanning graphene to dichalcogenides, and more recently 2D transition metal carbides (MXenes). One of the challenges now is to master ordering within the atomic sheets. Herein, we present a top-down, high-yield, facile route for the controlled introduction of ordered acancies in MXenes. By designing a parent 3D atomic laminate, (Mo 2/3 Sc 1/3 ) 2 AlC, with in-plane chemical ordering, and by selectively etching the Al and Sc atoms, we show evidence for 2D Mo 1.33 C sheets with ordered metal acancies and high electrical conductivities. At ∼1,100 F cm −3 , this 2D material exhibits a 65% higher volumetric capacitance than its counterpart, Mo 2 C, with no vacancies, and one of the highest volumetric capacitance values ever reported, to the best of our knowledge. This structural design on the atomic scale may alter and expand the concept of property-tailoring of 2D materials.
Publisher: Elsevier BV
Date: 07-2013
Publisher: Wiley
Date: 11-02-2202
Publisher: IOP Publishing
Date: 14-02-2017
Abstract: Inherently and artificially layered materials are commonly investigated both for fundamental scientific purposes and for technological application. When a layered material is thinned or delaminated to its physical limits, a two-dimensional (2D) material is formed and exhibits novel properties compared to its bulk parent phase. The complex layered phases known as ‘MAX phases’ (where M = early transition metal, A = A-group element, e.g. Al or Si, and X = C or N) are an exciting model system for materials design and the understanding of process-structure-property relationships. When the A layers are selectively etched from the MAX phases, a new type of 2D material is formed, named MXene to emphasize the relation to the MAX phases and the parallel with graphene. Since their discovery in 2011, MXenes have rapidly become established as a novel class of 2D materials with remarkable possibilities for composition variations and property tuning. This article gives a brief overview of MAX phases and MXene from a thin-film perspective, reviewing theory, characterization by electron microscopy, properties and how these are affected by the change in dimensionality, and outstanding challenges.
Publisher: Public Library of Science (PLoS)
Date: 15-10-2018
Publisher: AIP Publishing
Date: 11-11-2013
DOI: 10.1063/1.4830044
Abstract: Nucleation mechanism of catalyst-free GaN nanorod grown on Si(111) is investigated by the fabrication of uniform and narrow (& nm) nanorods without a pre-defined mask by molecular beam epitaxy. Direct evidences show that the nucleation of GaN nanorods stems from the sidewall of the underlying islands down to the Si(111) substrate, different from commonly reported ones on top of the island directly. Accordingly, the growth and density control of the nanorods is exploited by a “narrow-pass” approach that only narrow nanorod can be grown. The optimal size of surrounding non-nucleation area around single nanorod is estimated as 88 nm.
Publisher: MDPI AG
Date: 13-04-2020
DOI: 10.3390/MOLECULES25081782
Abstract: Lupin seeds are rich in proteins and other essential ingredients that can help to improve human health. The protein contents in both whole and split seeds of two lupin cultivars (Mandleup and PBA Jurien) were used to produce the lupin milk using the cheesecloth and centrifuge method. Proteins were extracted from the lupin milk using thiourea/urea solubilization. The proteins were separated by a two-dimensional polyacrylamide gel electrophoresis and then identified with mass spectrometry. A total of 230 protein spots were identified, 60 of which showed differential abundances. The cheesecloth separation showed protein extractability much better than that of the centrifuge method for both the cultivars. The results from this study could offer guidance for future comparative analysis and identification of lupin milk protein and provide effective separation technique to determine specific proteins in the cheese-making process.
Publisher: American Chemical Society (ACS)
Date: 13-10-2020
DOI: 10.1021/JACS.0C08113
Publisher: IEEE
Date: 2005
Publisher: American Physical Society (APS)
Date: 20-09-2018
Publisher: Elsevier BV
Date: 03-2004
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NR02354B
Abstract: We report the synthesis and characterization of a new laminated i-MAX phase, (V 2/3 Sc 1/3 ) 2 AlC, with in-plane chemical ordering between the M-elements. We also produce V 2−x C MXene with only 24 h etching time using HF and MXene scrolls using LiF + HCl.
Publisher: American Chemical Society (ACS)
Date: 11-12-2014
DOI: 10.1021/NL503564K
Abstract: Chirality, tailored by external morphology and internal composition, has been realized by controlled curved-lattice epitaxial growth of In(x)Al(1-x)N nanospirals. The curved morphology of the spiral segments is a result of a lateral compositional gradient while maintaining a preferred crystallographic growth direction, implying a lateral gradient in optical properties. In idual nanospirals show an asymmetric core-shell structure with curved basal planes. Mueller matrix spectroscopic ellipsometry shows that the tailored chirality is manifested in the polarization state of light reflected off the nanospirals.
Publisher: American Physical Society (APS)
Date: 24-05-2018
Publisher: AIP Publishing
Date: 05-2022
DOI: 10.1063/5.0087571
Abstract: The hot-wall metalorganic chemical vapor deposition (MOCVD) concept, previously shown to enable superior material quality and high performance devices based on wide bandgap semiconductors, such as Ga(Al)N and SiC, has been applied to the epitaxial growth of β-Ga2O3. Epitaxial β-Ga2O3 layers at high growth rates (above 1 μm/h), at low reagent flows, and at reduced growth temperatures (740 °C) are demonstrated. A high crystalline quality epitaxial material on a c-plane sapphire substrate is attained as corroborated by a combination of x-ray diffraction, high-resolution scanning transmission electron microscopy, and spectroscopic ellipsometry measurements. The hot-wall MOCVD process is transferred to homoepitaxy, and single-crystalline homoepitaxial β-Ga2O3 layers are demonstrated with a 2̄01 rocking curve width of 118 arc sec, which is comparable to those of the edge-defined film-fed grown (2̄01) β-Ga2O3 substrates, indicative of similar dislocation densities for epilayers and substrates. Hence, hot-wall MOCVD is proposed as a prospective growth method to be further explored for the fabrication of β-Ga2O3.
Publisher: Elsevier BV
Date: 2017
Publisher: AIP Publishing
Date: 15-03-2002
DOI: 10.1063/1.1448886
Abstract: Epitaxial aluminum nitride thin films have been grown on silicon carbide (6H-SiC) substrates by pulsed low-energy ion-assisted reactive magnetron sputter deposition (+5/−20 V of bias pulses), with ion-assisted energy (Ei)≅22 eV, under ultrahigh-vacuum conditions. Surface ion interactions during the negative bias pulse gave rise to enhanced surface mobility of adatoms with beneficial effects, which extended over the limit of ion repelling in the positive pulse as the film thickness increased. High-resolution electron microscopy shows that a large (& nm) AlN domain width can form on the substrate. Domain-boundary annihilation and domain suppression during film growth have been observed. The growth rate also increased by a factor of ∼4 compared to growth conditions with no ion assistance (Ei=2 eV) and by a factor of 2 from dc ion-assisted growth. This indicates that the supply of nitrogen is a limiting factor for AlN formation and that the reactivity of nitrogen is increased on the growing AlN film surface for pulse ion-assisted deposition. High-resolution x-ray diffraction shows a reduction in the full width at half maximum of the rocking curve from 1490 to 1180 arcsec when pulsed ions are used. The cathodoluminescence shows high intensity of near-band edge emissions at wavelengths of 206 (6.02 eV) and 212 nm (5.84 eV) at a measured temperature of 5 K, with relatively low defect and oxygen and carbon impurity related emission, which is indicative of a high quality electronic material.
Publisher: Wiley
Date: 18-02-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0TA00687D
Abstract: MXene based all-solution processed semitransparent flexible photovoltaic supercapacitor was fabricated by integrating the flexible organic photovoltaic with MXene as the electrode and transparent MXene supercapacitors in the vertical direction.
Publisher: American Chemical Society (ACS)
Date: 08-01-2021
Publisher: Elsevier BV
Date: 09-2001
Publisher: Elsevier BV
Date: 02-2006
DOI: 10.1016/J.JCIS.2005.07.013
Abstract: The competitive adsorption between oxalate and malonate at the water-goethite interface was studied as a function of pH and total ligand concentrations by means of quantitative adsorption measurements and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The results obtained show that ATR-FTIR spectroscopy resolves the in idual spectroscopic features of oxalate and malonate when adsorbed simultaneously at the water-goethite interface. The characteristic peaks of all four types of predominating surface complexes existing in the single ligand systems were identified, namely one inner sphere and one outer sphere surface complex for each ligand. The quantitative adsorption data showed that oxalate partially out-competes malonate at the water-goethite interface. Evaluation of the peak area variations as a function of pH indicated that the stronger oxalate adsorption can be ascribed to the more stable inner sphere surface complex of oxalate, which in turn is related to the oxalate five-member chelate ring structure yielding a more stable complex compared to the six-member ring of malonate.
Publisher: Elsevier BV
Date: 12-2019
Publisher: Elsevier BV
Date: 2002
Publisher: AIP Publishing
Date: 06-10-2008
DOI: 10.1063/1.2998588
Abstract: Cubic metastable Ti0.34Al0.66N/TiN multilayers were grown by reactive arc evaporation using Ti33–Al67 and Ti cathodes in a N2 atmosphere. X-ray diffractometry and high resolution transmission electron microscopy revealed that metastable c-Ti0.34Al0.66N partly decomposes after annealing at 900 °C into c-TiN rich and c-AlN rich phases with retained lattice coherency. Elemental mapping by energy dispersive x-ray spectroscopy showed a homogenous distribution of Ti and Al in the as-deposited 25 nm Ti0.34Al0.66N layers. The annealed Ti0.34Al0.66N layers exhibited coherent 5 nm domains with high Al content surrounded by a high Ti content matrix. This nanostructure formation is discussed in terms of spinodal decomposition.
Publisher: Elsevier BV
Date: 11-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7NR00916J
Abstract: In this work we report strategies to nucleate bimetallic nanoparticles (NPs) made by gas phase synthesis of elements showing difficulty in homogeneous nucleation. It is shown that the nucleation assisted problem of bimetallic NP synthesis can be solved via the following pathways: (i) selecting an element which can itself nucleate and act as a nucleation center for the synthesis of bimetallic NPs (ii) introducing H
Publisher: Elsevier BV
Date: 02-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8RA07270A
Abstract: Ti 3 C 2 T x (MXene) thin film shows elimination of –F and domination of –O surface terminations after NaOH treatment followed by annealing while preserving the electrical conductivity of the film.
Publisher: American Physical Society (APS)
Date: 05-05-2023
Publisher: American Chemical Society (ACS)
Date: 23-05-2023
Publisher: Elsevier BV
Date: 05-2021
Publisher: American Chemical Society (ACS)
Date: 05-04-2023
Publisher: American Physical Society (APS)
Date: 12-01-2022
Publisher: Wiley
Date: 11-04-2005
Publisher: AIP Publishing
Date: 31-03-2005
DOI: 10.1063/1.1870111
Abstract: Ternary wurtzite Al1−xInxN thin films with compositions throughout the miscibility gap have been grown onto seed layers of TiN and ZrN by magnetron sputter epitaxy (MSE) using dual reactive direct current magnetron sputter deposition under ultra high vacuum conditions. The film compositions were calculated using Vegard’s law from lattice parameters determined by x-ray diffraction (XRD). XRD showed that single-phase Al1−xInxN alloy films in the wurtzite structure with [0.10& x& .90] could be obtained at substrate temperatures up to 600°C by heteroepitaxial growth. Epitaxial growth at 600°C gave the crystallographic relations Al1−xInxN(0001)∕∕TiN,ZrN(111) and Al1−xInxN⟨10-10⟩∕∕TiN,ZrN⟨110⟩. At higher substrate temperatures almost pure AlN was formed. The microstructure of the films was also investigated by high-resolution electron microscopy. A columnar growth mode with epitaxial column widths from 10to200nm was observed. Rocking curve full-width-at-half-maximum measurements revealed highly stressed lattices for growth onto TiN at 600°C. Pseudobinary MSE growth phase field diagrams for Al1−xInxN onto ZrN and TiN were established for substrate temperatures up to 1000°C. Large regimes for single-phase solid solutions were thus identified with In being the diffusing species.
Publisher: AIP Publishing
Date: 02-2022
DOI: 10.1063/5.0074010
Abstract: We investigate the interfaces and polarity domains at the atomic scale in epitaxial AlN and GaN/AlN grown by hot-wall metal organic chemical vapor epitaxy on the carbon face of SiC. X-ray diffraction, potassium hydroxide (KOH) wet chemical etching, and scanning transmission electron microscopy combined provide an in-depth understanding of polarity evolution with the film thickness, which is crucial to optimize growth. The AlN grown in a 3D mode is found to exhibit N-polar pyramid-type structures at the AlN–SiC interface. However, a mixed N-polar and Al-polar region with Al-polarity domination along with inverted pyramid-type structures evolve with increasing film thickness. We identify inclined inversion domain boundaries and propose that incorporation of oxygen on the ⟨40–41⟩ facets of the N-polar pyramids causes the polarity inversion. We find that mixed-polar AlN is common and easily etched and remains undetected by solely relying on KOH etching. Atomic scale electron microscopy is, therefore, needed to accurately determine the polarity. The polarity of GaN grown on mixed-polar AlN is further shown to undergo complex evolution with the film thickness, which is discussed in the light of growth mechanisms and polarity determination methods.
Publisher: American Physical Society (APS)
Date: 15-09-2009
Publisher: Informa UK Limited
Date: 05-2011
Publisher: Wiley
Date: 14-06-2022
Abstract: Aqueous asymmetric supercapacitors (AASCs) can have high voltages and high energy densities. However, the rational design of AASCs with proper negative and positive electrodes remains a challenge. Herein, we report on an AASC using Mo 1.33 CT z MXene films as the negative electrode, and tetramethylammonium cation intercalated birnessite (TMA + ‐MnO 2 ) films as the positive electrode in a 21 mol kg −1 lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) electrolyte. Benefiting from a high, stable voltage of 2.5 V, an energy density of 86.5 Wh L −1 at 2 mV s −1 and a power density of 10.3 kW L −1 at 1 V s −1 were achieved. The cells also exhibit excellent cycling stability ( % after 1,0000 cycles at 100 mV s −1 ) and a 51.1 % voltage retention after 10 h. This good performance is attributed to the high stable potential window and high volumetric capacitances of both Mo 1.33 CT z and TMA + ‐MnO 2 electrodes in highly concentrated electrolytes. This work provides a roadmap for developing high performance AASCs with high voltages and high energy ower densities, with relatively slow self‐discharge rates.
Publisher: Elsevier BV
Date: 2021
Publisher: AIP Publishing
Date: 08-2006
DOI: 10.1063/1.2219380
Abstract: The crystal structure and optical properties of thick (& nm) AlN layers grown by hot-wall metalorganic chemical vapor deposition are characterized by infrared spectroscopic ellipsometry, cathodoluminescence, and transmission electron microscopy. The choice of substrates among the available SiC wafer polytype modifications (4H∕6H) and misorientations (on-/off-axis cut) is found to determine the AlN defect interaction, stress homogeneity, and luminescence. The growth of thick AlN layers benefits by performing the epitaxy on off-axis substrates because, due to stacking faults, the propagation of threading defects in AlN layers is stopped in a narrow interface region.
Publisher: Wiley
Date: 12-2002
DOI: 10.1002/1521-396X(200212)194:2<532::AID-PSSA532>3.0.CO;2-R
Publisher: Wiley
Date: 04-11-2018
Abstract: Global warming caused by burning of fossil fuels is indisputably one of mankind's greatest challenges in the 21st century. To reduce the ever-increasing CO
Publisher: IOP Publishing
Date: 11-11-2009
DOI: 10.1088/0957-4484/20/49/495304
Abstract: Highly oriented AlN single crystal nanowires with aspect ratio up to 600, diameter in the range of 40-500 nm, and 100 microm lengths, have been synthesized via a vapor-solid growth mechanism. The results were obtained at 1750 degrees C and 850 mbar nitrogen pressure on vicinal SiC substrates pretreated by SiC sublimation epitaxy in order to attain distinguishable terraces. It was found that the nanowires change in thickness after they have reached a critical length, and this fact contributes to an understanding of the growth mechanism of AlN nanowires. The nanowires are hexagonally shaped and perfectly aligned along the [0001] direction with a small tilt given by the substrate vicinality. Under nitrogen excess a preferential growth along the c-axis of the wurtzite structure takes place while below some critical value of nitrogen pressure the growth mode switches to lateral. The AlN nanowires are shown to have a dislocation free wurtzite crystal structure. Some possible applications are discussed.
Publisher: Elsevier BV
Date: 2003
Publisher: Cold Spring Harbor Laboratory
Date: 03-09-2018
DOI: 10.1101/406694
Abstract: Wheat Avenin-like proteins (TaALP) are atypical storage proteins belonging to the Prolamin superfamily. Previous studies on ALPs have focused on the proteins’ positive effects on dough strength, whilst no correlation has been made between TaALPs and the plant immune system. Here, we performed genome-wide characterization of ALP encoding genes in bread wheat. In silico analyses indicated the presence of critical peptides in TaALPs that are active in the plant immune system. Pathogenesis-related nucleotide motifs were also identified in the putative promoter regions of TaALP encoding genes. RT-PCR was performed on TaALP and previously characterised pathogenesis resistance genes in developing wheat caryopses under control and Fusarium graminearum infection conditions. The results showed that TaALP and NMT genes were upregulated upon F. graminearum inoculation. mRNA insitu hybridization showed that TaALP genes were expressed in the embryo, aleurone and sub-aleurone layer cells. Seven TaALP genes were cloned for the expression of recombinant proteins in Escherichia coli , which displayed significant inhibitory function on F. graminearum under anti-fungal tests. In addition, FHB index association analyses showed that allelic variations of two ALP genes on chromosome 7A were significantly correlated with FHB symptoms. Over-expression of an ALP gene on chromosome 7A showed an enhanced resistance to FHB. Yeast two Hybridization results revealed that ALPs have potential proteases inhibiting effect on metacaspases and beta-glucosidases. A vital infection process related pathogen protein, F. graminearum Beta-glucosidase was found to interact with ALPs. Our study is the first to report a class of wheat storage protein or gluten protein with biochemical functions. Due to its abundance in the grain and the important multi-functions, the results obtained in the current study are expected to have a significant impact on wheat research and industry.
Publisher: AIP Publishing
Date: 05-2012
DOI: 10.1063/1.4714220
Abstract: Piezoelectric wurtzite ScxAl1−xN (x = 0, 0.1, 0.2, 0.3) thin films were epitaxially grown by reactive magnetron co-sputtering from elemental Sc and Al targets. Al2O3(0001) wafers with TiN(111) seed and electrode layers were used as substrates. X-ray diffraction shows that an increase in the Sc content results in the degradation of the crystalline quality. S les grown at 400 °C possess true dielectric behavior with quite low dielectric losses and the leakage current is negligible. For ScAlN s les grown at 800 °C, the crystal structure is poor and leakage current is high. Transmission electron microscopy with energy dispersive x-ray spectroscopy mapping shows a mass separation into ScN-rich and AlN-rich domains for x ≥ 0.2 when substrate temperature is increased from 400 to 800 °C. The piezoelectric response of epitaxial ScxAl1−xN films measured by piezoresponse force microscopy and double beam interferometry shows up to 180% increase by the addition of Sc up to x = 0.2 independent of substrate temperature, in good agreement with previous theoretical predictions based on density-functional theory.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7NR03663A
Abstract: Au-containing nanolaminated carbides Mo 2 AuC and Mo 2 (Au 1−x Ga x ) 2 C were synthesized by a thermally induced substitutional reaction in Mo 2 GaC and Mo 2 Ga 2 C, respectively.
Publisher: Springer Science and Business Media LLC
Date: 11-2007
Abstract: We report the layer structure and composition in recently discovered TiN/SiN(001) superlattices deposited by dual-reactive magnetron sputtering on MgO(001) substrates. High-resolution transmission electron microscopy combined with Z -contrast scanning transmission electron microscopy, x-ray reflection, diffraction, and reciprocal-space mapping shows the formation of high-quality superlattices with coherently strained cubic TiN and SiN layers for SiN thickness below 7–10 Å. For increasing SiN layer thicknesses, a transformation from epitaxial to amorphous SiN x ( x ⩾ 1) occurs during growth. Elastic recoil detection analysis revealed an increase in nitrogen and argon content in SiN x layers during the phase transformation. The oxygen, carbon, and hydrogen contents in the multilayers were around the detection limit (∼0.1 at.%) with no indication of segregation to the layer interfaces. Nanoindentation experiments confirmed superlattice hardening in the films. The highest hardness of 40.4 ± 0.8 GPa was obtained for 20-Å TiN with 5-Å-thick SiN(001) interlayers, compared to monolithic TiN at 20.2 ± 0.9 GPa.
Publisher: AIP Publishing
Date: 12-01-2009
DOI: 10.1063/1.3065030
Abstract: The free electron behavior in InN is studied on the basis of decoupled bulk and surface accumulation electron densities in InN films measured by contactless optical Hall effect. It is shown that the variation in the bulk electron density with film thickness does not follow the models of free electrons generated by dislocation-associated nitrogen vacancies. This finding, further supported by transmission electron microscopy results, indicates the existence of a different thickness-dependent doping mechanism. Furthermore, we observe a noticeable dependence of the surface electron density on the bulk density, which can be exploited for tuning the surface charge in future InN based devices.
Publisher: AIP Publishing
Date: 11-2014
DOI: 10.1063/1.4901125
Publisher: AIP Publishing
Date: 25-02-2016
DOI: 10.1063/1.4942664
Abstract: The phase formation in the boron-rich section of the Al-Y-B system has been explored by a correlative theoretical and experimental research approach. The structure of coatings deposited via high power pulsed magnetron sputtering from a compound target was studied using elastic recoil detection analysis, electron energy loss spectroscopy spectrum imaging, as well as X-ray and electron diffraction data. The formation of AlYB14 together with the (Y,Al)B6 impurity phase, containing 1.8 at. % less B than AlYB14, was observed at a growth temperature of 800 °C and hence 600 °C below the bulk synthesis temperature. Based on quantum mechanical calculations, we infer that minute compositional variations within the film may be responsible for the formation of both icosahedrally bonded AlYB14 and cubic (Y,Al)B6 phases. These findings are relevant for synthesis attempts of all boron rich icosahedrally bonded compounds with the space group: Imma that form ternary phases at similar compositions.
Publisher: Wiley
Date: 18-07-2022
Abstract: Solid‐state precipitation can be used to tailor material properties, ranging from ferromagnets and catalysts to mechanical strengthening and energy storage. Thermoelectric properties can be modified by precipitation to enhance phonon scattering while retaining charge‐carrier transmission. Here, unconventional Janus‐type nanoprecipitates are uncovered in Mg 3 Sb 1.5 Bi 0.5 formed by side‐by‐side Bi‐ and Ge‐rich appendages, in contrast to separate nanoprecipitate formation. These Janus nanoprecipitates result from local comelting of Bi and Ge during sintering, enabling an amorphous‐like lattice thermal conductivity. A precipitate size effect on phonon scattering is observed due to the balance between alloy‐disorder and nanoprecipitate scattering. The thermoelectric figure‐of‐merit ZT reaches 0.6 near room temperature and 1.6 at 773 K. The Janus nanoprecipitation can be introduced into other materials and may act as a general property‐tailoring mechanism.
Publisher: American Chemical Society (ACS)
Date: 10-01-2023
Publisher: Elsevier BV
Date: 03-2022
Publisher: American Chemical Society (ACS)
Date: 23-09-2019
Publisher: Wiley
Date: 22-12-2010
Publisher: MDPI AG
Date: 02-09-2017
DOI: 10.3390/EN10091322
Abstract: We demonstrate the versatility of magnetron sputter epitaxy by achieving high-quality GaN nanorods on different substrate/template combinations, specifically Si, SiC, TiN/Si, ZrB2/Si, ZrB2/SiC, Mo, and Ti. Growth temperature was optimized on Si, TiN/Si, and ZrB2/Si, resulting in increased nanorod aspect ratio with temperature. All nanorods exhibit high purity and quality, proved by the strong bandedge emission recorded with cathodoluminescence spectroscopy at room temperature as well as transmission electron microscopy. These substrates/templates are affordable compared to many conventional substrates, and the direct deposition onto them eliminates cumbersome post-processing steps in device fabrication. Thus, magnetron sputter epitaxy offers an attractive alternative for simple and affordable fabrication in optoelectronic device technology.
Publisher: Elsevier BV
Date: 04-2008
Publisher: American Chemical Society (ACS)
Date: 19-01-2023
Publisher: AIP Publishing
Date: 10-07-2023
DOI: 10.1063/5.0150863
Abstract: Structural defects are detrimental to the efficiency and quality of optoelectronic semiconductor devices. In this work, we study InGaN platelets with a quantum well structure intended for nano-LEDs emitting red light and how their optical properties, measured with cathodoluminescence, relate to the corresponding atomic structure. Through a method of spectroscopy–thinning–imaging, we demonstrate in plan-view how stacking mismatch boundaries intersect the quantum well in a pattern correlated with the observed diminished cathodoluminescence intensity. The results highlight the importance of avoiding stacking mismatch in small LED structures due to the relatively large region of non-radiative recombination caused by the mismatch boundaries.
Publisher: Elsevier BV
Date: 05-2020
DOI: 10.1016/J.FOODCHEM.2019.126038
Abstract: To understand wheat dough protein behavior under dual mixing and thermal treatment, solubility of Mixolab-dough proteins were investigated using nine extraction buffers of different dissociation capacities. Size exclusion high performance liquid chromatography (SE-HPLC) and two-dimensional gel electrophoresis (2-DGE) demonstrated that overall changes of protein fractions and dynamic responses of specific proteins during dough processing were well reflected by their solubility variations. After starch pasting, the abundance of 0.5 M NaCl extractable proteins were decreased except for six protein groups including α-amylase inhibitors and superoxide dismutase (SOD). The solubility loss of glutenin proteins at C3 (32 min 80 ℃) was mainly ascribed to the un-extractable HMW-GSs, LMW-GSs, globulin and triticin, while the extract yield of α-, β-, γ-gliadins and avenin-like proteins (ALPs) increased after starch pasting. Differential responses of dough proteins to extraction systems provides the basis for further exploring wheat protein dynamics in processing.
Publisher: Wiley
Date: 10-2021
Abstract: Organic electrochemical transistors (OECTs) have the potential to revolutionize the field of organic bioelectronics. To date, most of the reported OECTs include p‐type (semi‐)conducting polymers as the channel material, while n‐type OECTs are yet at an early stage of development, with the best performing electron‐transporting materials still suffering from low transconductance, low electron mobility, and slow response time. Here, the high electrical conductivity of multi‐walled carbon nanotubes (MWCNTs) and the large volumetric capacitance of the ladder‐type π‐conjugated redox polymer poly(benzimidazobenzophenanthroline) (BBL) are leveraged to develop n‐type OECTs with record‐high performance. It is demonstrated that the use of MWCNTs enhances the electron mobility by more than one order of magnitude, yielding fast transistor transient response (down to 15 ms) and high μC * (electron mobility × volumetric capacitance) of about 1 F cm −1 V −1 s −1 . This enables the development of complementary inverters with a voltage gain of and a large worst‐case noise margin at a supply voltage of .6 V, while consuming less than 1 µW of power.
Publisher: Elsevier BV
Date: 10-2000
Publisher: AIP Publishing
Date: 11-05-2022
DOI: 10.1063/5.0089406
Abstract: The hot-wall metal-organic chemical vapor deposition (MOCVD), previously shown to enable superior III-nitride material quality and high performance devices, has been explored for Mg doping of GaN. We have investigated the Mg incorporation in a wide doping range (2.45×1018 cm−3 up to 1.10×1020 cm−3) and demonstrate GaN:Mg with low background impurity concentrations under optimized growth conditions. Dopant and impurity levels are discussed in view of Ga supersaturation, which provides a unified concept to explain the complexity of growth conditions impact on Mg acceptor incorporation and compensation. The results are analyzed in relation to the extended defects, revealed by scanning transmission electron microscopy, x-ray diffraction, and surface morphology, and in correlation with the electrical properties obtained by Hall effect and capacitance–voltage (C–V) measurements. This allows to establish a comprehensive picture of GaN:Mg growth by hot-wall MOCVD providing guidance for growth parameters optimization depending on the targeted application. We show that substantially lower H concentration as compared to Mg acceptors can be achieved in GaN:Mg without any in situ or post-growth annealing resulting in p-type conductivity in as-grown material. State-of-the-art p-GaN layers with a low resistivity and a high free-hole density (0.77 Ω cm and 8.4×1017 cm−3, respectively) are obtained after post-growth annealing demonstrating the viability of hot-wall MOCVD for growth of power electronic device structures.
Publisher: Proceedings of the National Academy of Sciences
Date: 10-12-2018
Abstract: Fifteen full-length wheat grain avenin-like protein coding genes ( TaALP ) were identified on chromosome arms 7AS, 4AL, and 7DS of bread wheat with each containing five genes. Besides the a- and b-type ALPs, a c type was identified in the current paper. Both a and b types have two subunits, named x and y types. The five genes on each of the three chromosome arms consisted of two x-type genes, two y-type genes, and one c-type gene. The a-type genes were typically of 520 bp in length, whereas the b types were of 850 bp in length, and the c type was of 470 bp in length. The ALP gene transcript levels were significantly up-regulated in Blumeria graminis f. sp. tritici (Bgt) -infected wheat grain caryopsis at early grain filling. Wild emmer wheat [(WEW), Triticum dicoccoides ] populations were focused on in our paper to identify allelic variations of ALP genes and to study the influence of natural selection on certain alleles. Consequently, 25 alleles were identified for TdALP-bx-7AS , 13 alleles were identified for TdALP-ax-7AS , 7 alleles were identified for TdALP-ay-7AS , and 4 alleles were identified for TdALP-ax-4AL . Correlation studies on TdALP gene ersity and ecological stresses suggested that environmental factors contribute to the ALP polymorphism formation in WEW. Many allelic variants of ALPs in the endosperm of WEW are not present in bread wheat and therefore could be utilized in breeding bread wheat varieties for better quality and elite plant defense characteristics.
Publisher: American Chemical Society (ACS)
Date: 06-07-2020
DOI: 10.26434/CHEMRXIV.12608681.V1
Abstract: In the present research article we report synthesis of TiB x , 1.43 n-situ mass- and energy-spectroscopy is used to explain the obtained compositional range. Excess B in overstoichiometric TiB x thin films from DCMS results in a hardness up to 37.7±0.8 GPa, attributed to the formation of an amorphous B-rich tissue phase separating stoichiometric TiB 2 columnar structures. With a particular focus on characterization of the understoichiometric s les, we show that understoichiometric TiB 1.43 thin films synthesized by HiPIMS exhibit a superior hardness of 43.9±0.9 GPa, where the deficiency of B is found to be accommodated by Ti planar defects. The apparent fracture toughness, electrical resistivity and thermal conductivity of the same s le is 4.2±0.1 MPa√m, 367±7 μΩ·cm and 5.1 W/(m.K), respectively, as compared to corresponding values for overstoichiometric TiB 2.20 DCMS thin film s les of 3.2±0.1 MPa√m, 309±4 μΩ·cm and 3.0 W/(m.K).
Publisher: Elsevier BV
Date: 12-1993
Publisher: Elsevier BV
Date: 10-2016
Publisher: IOP Publishing
Date: 20-02-2019
Publisher: Wiley
Date: 23-10-2018
DOI: 10.1111/TPJ.14096
Abstract: In wheat (Triticum aestivum) grain yield and grain protein content are negatively correlated, making the simultaneous increase of the two traits challenging. Apart from genetic approaches, modification of nitrogen fertilization offers a feasible option to achieve this aim. In this study, a range of traits related to nitrogen-use efficiency in six Australian bread wheat varieties were investigated under different nitrogen treatments using 3-year multisite field trials. Changes in the in idual storage protein composition were detected by high-performance liquid chromatography. Our results indicated that wheat grain yield and grain protein content reacted similarly to nitrogen availability, with grain yield being slightly more sensitive than grain protein content, and that genotype is a vital determinant of grain protein yield. Measurement of the glutamine synthetase activity of flag leaves and developing grains revealed that high nitrogen availability prompted the participation of glutamine in biological processes. In addition, a more significant accumulation of gluten macropolymer was observed under the high-nitrogen treatment from 21 days post-anthesis, and the underlying mechanism was elucidated by a comparative proteomics study. A yeast two-hybrid experiment confirmed this mechanism. The results of this study revealed that peptidyl-prolyl cis-trans isomerase (PPIase) was SUMOylated with the assistance of small ubiquitin-related modifier 1 and that high nitrogen availability facilitated this connection for the subsequent protein polymerization. Additionally, luminal-binding protein 2 in the endoplasmic reticulum played a similar role to PPIase in the aggregation of protein under high-nitrogen conditions.
Publisher: Constructive Mathematical Analysis
Date: 03-2021
DOI: 10.33205/CMA.844390
Abstract: We laconically describe the great contributions of Professor Francesco Altomare to mathematical research and PhD education, and his unique status in the mathematical community. In particular, we present and give ex les of his innovative and great achievements related to the following areas of mathematics: Functional Analysis, Operator Theory, Potential Theory, Approximation Theory, Probability Theory, Function Spaces, Choquet's Theory, Dirichlet's Problem and Semigroup Theory. Moreover, we report on and give concrete ex les of his unique way to work together with PhD students, both before and sometimes also after their dissertation. Finally, we shortly describe his remarkable “class travel” from “simple” conditions with no academic traditions in his family in the small hometown Giovinazzo to finally become the broad, ingenious, and powerful mathematician he is regarded to be today.
Publisher: The Electrochemical Society
Date: 25-09-2009
DOI: 10.1149/1.3207674
Abstract: AlxGa1-xN multiple quantum wells (MQW) were grown on AlN epilayer grown on 4H-SiC substrate. The growth was performed without interruption in a horizontal hot-wall MOCVD reactor using a mixture of hydrogen and nitrogen as carrier gases. The precursors were ammonia, trimethylaluminum and trimethylgallium. Results obtained from X-ray diffraction and infra-red reflectance were used to obtain the composition of the films when growing simple AlxGa1 xN layer. Visible reflectance was used to evaluate the thickness of the films. Finally the MQW parameters as thicknesses and composition variation were obtained by scanning transmission electron microscopy and demonstrated an agreement with the growth parameters used
Publisher: Wiley
Date: 08-10-2023
Publisher: AIP Publishing
Date: 24-02-2015
DOI: 10.1063/1.4908216
Abstract: Understanding and controlling growth of graphene on the carbon face (C-face) of SiC presents a significant challenge. In this work, we study the structural, vibrational, and dielectric function properties of graphene grown on the C-face of 4H-SiC by high-temperature sublimation in an argon atmosphere. The effect of growth temperature on the graphene number of layers and crystallite size is investigated and discussed in relation to graphene coverage and thickness homogeneity. An amorphous carbon layer at the interface between SiC and the graphene is identified, and its evolution with growth temperature is established. Atomic force microscopy, micro-Raman scattering spectroscopy, spectroscopic ellipsometry, and high-resolution cross-sectional transmission electron microscopy are combined to determine and correlate thickness, stacking order, dielectric function, and interface properties of graphene. The role of surface defects and growth temperature on the graphene growth mechanism and stacking is discussed, and a conclusion about the critical factors to achieve decoupled graphene layers is drawn.
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 04-2016
Publisher: American Association for the Advancement of Science (AAAS)
Date: 13-08-2021
Abstract: A range of two-dimensional (2D) materials, including graphene and hexagonal boron nitride, have been synthesized and studied because of the unusual properties that occur when one dimension becomes very small. MXenes are a family of materials made of layers of inorganic transition metal carbides and nitrides that are a few atoms thick and are manufactured by selective etching. Attempts to make similar boridene materials have been challenging because of the reactive nature of boride phases and because the parent materials tend to dissolve rather than selectively etch. Zhou et al . synthesized boridene in the form of single-layer 2D molybdenum boride sheets by selective etching in aqueous hydrofluoric acid to produce sheets with ordered metal vacancies, opening up an additional family of materials for study. —MSL
Publisher: Springer Science and Business Media LLC
Date: 26-10-2022
DOI: 10.1038/S41598-022-22622-1
Abstract: Structural defects in Mg-doped GaN were analyzed using high-resolution scanning transmission electron microscopy combined with electron energy loss spectroscopy. The defects, in the shape of inverted pyramids, appear at high concentrations of incorporated Mg, which also lead to a reduction in free-hole concentration in Mg doped GaN. Detailed analysis pinpoints the arrangement of atoms in and around the defects and verify the presence of a well-defined layer of Mg at all facets, including the inclined facets. Our observations have resulted in a model of the pyramid-shaped defect, including structural displacements and compositional replacements, which is verified by image simulations. Finally, the total concentration of Mg atoms bound to these defects were evaluated, enabling a correlation between inactive and defect-bound dopants.
Publisher: Elsevier BV
Date: 03-2017
Publisher: IOP Publishing
Date: 04-10-2012
DOI: 10.1088/0022-3727/45/42/422001
Abstract: Reactive magnetron sputtering was used to deposit Y x Al 1− x N thin films, 0 ⩽ x ⩽ 0.22, onto Al 2 O 3 (0 0 0 1) and Si(1 0 0) substrates. X-ray diffraction and analytical electron microscopy show that the films are solid solutions. Lattice constants increase with Y concentration, in agreement with ab initio calculations. Spectroscopic ellipsometry measurements reveal a band gap decrease from 6.2 eV ( x = 0) down to 4.5 eV ( x = 0.22). Theoretical investigations within the special quasirandom structure approach show that the wurtzite structure has the lowest mixing enthalpy for 0 ⩽ x ⩽ 0.75.
Publisher: Elsevier BV
Date: 05-2020
Publisher: AIP Publishing
Date: 09-12-2013
DOI: 10.1063/1.4838495
Abstract: ZrN/SiNx nanoscale multilayers were deposited on ZrN seed layers grown on top of MgO(001) substrates by dc magnetron sputtering with a constant ZrN thickness of 40 Å and with an intended SiNx thickness of 2, 4, 6, 8, and 15 Å at a substrate temperature of 800 °C and 6 Å at 500 °C. The films were investigated by X-ray diffraction, high-resolution scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy. The investigations show that the SiNx is amorphous and that the ZrN layers are crystalline. Growth of epitaxial cubic SiNx—known to take place on TiN(001)—on ZrN(001) is excluded to the monolayer resolution of this study. During the course of SiNx deposition, the material segregates to form surface precipitates in discontinuous layers for SiNx thicknesses ≤6 Å that coalesce into continuous layers for 8 and 15 Å thickness at 800 °C, and for 6 Å at 500 °C. The SiNx precipitates are aligned vertically. The ZrN layers in turn grow by epitaxial lateral overgrowth on the discontinuous SiNx in s les deposited at 800 °C with up to 6 Å thick SiNx layers. Effectively a self-organized nanostructure can be grown consisting of strings of 1–3 nm large SiNx precipitates along apparent column boundaries in the epitaxial ZrN.
Publisher: IOP Publishing
Date: 21-03-2014
Publisher: American Chemical Society (ACS)
Date: 29-08-2014
DOI: 10.1021/NL502281P
Abstract: The III-V semiconductor nanowires (NWs) have a great potential for applications in a variety of future electronic and photonic devices with enhanced functionality. In this work, we employ polarization-resolved microphotoluminescence (μ-PL) spectroscopy to study polarization properties of light emissions from in idual GaNP and GaP/GaNP core/shell NWs with average diameters ranging between 100 and 350 nm. We show that the near-band-edge emission, which originates from the GaNP regions of the NWs, is strongly polarized (up to 60% at 150 K) in the direction perpendicular to the NW axis. The polarization anisotropy can be retained up to room temperature. This polarization behavior, which is unusual for zinc blende NWs, is attributed to local strain in the vicinity of the N-related centers participating in the radiative recombination and to preferential alignment of their principal axis along the growth direction. Our findings therefore show that defect engineering via alloying with nitrogen provides an additional degree of freedom to tailor the polarization anisotropy of III-V nanowires, which is advantageous for their applications as nanoscale emitters of polarized light.
Publisher: AIP Publishing
Date: 19-02-2004
DOI: 10.1063/1.1645996
Abstract: The influence of carbon and germanium on phase transformation and sheet resistance of Ni on epitaxially grown Si1−x−yGexCy (0⩽x⩽0.24 and 0⩽y⩽0.01) layers annealed in a temperature range of 360 to 900 °C has been investigated. The role of strain relaxation or compensation in the reaction of Ni on Si1−x−yGexCy layers due to Ge or C out-diffusion to the underlying layer during the phase transformation has also been investigated. The formed NiSiGe layers were crystalline, with strong (020)/(013) growth orientation in the direction, but the thermal stability decreased rapidly with increasing Ge amount due to agglomeration. However, this thermal behavior was shifted to higher annealing temperatures when carbon was incorporated in the SiGe layers. A carbon accumulation at the interface of NiSiGeC/SiGeC has been observed even at low-temperature annealing, which is suggested to retard the phase transformation and agglomeration of Ni/SiGeC system.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Elsevier BV
Date: 06-2006
Publisher: Informa UK Limited
Date: 09-12-2013
Publisher: AIP Publishing
Date: 15-03-2008
DOI: 10.1063/1.2896637
Abstract: Ti C x thin films were deposited on Al2O3 substrates at 900°C by using a multiple cathode high current pulsed cathodic arc. The Ti:C pulse ratio and, hence, the composition was varied from C rich to Ti rich. It is found that the Al2O3 substrate is decomposed and reacts with the TiCx film to incorporate significant amounts of O and Al in the growing film. When the stoichiometry is suitable, epitaxially oriented Ti2AlC MAX phase with significant O incorporated is formed. The results indicate that Al2O3 is not an ideal substrate material for the growth of transition metal carbides and MAX phase thin films.
Publisher: Springer Science and Business Media LLC
Date: 24-09-2018
Publisher: AIP Publishing
Date: 03-2007
DOI: 10.1063/1.2709571
Abstract: A multicathode high current pulsed cathodic arc has been used to deposit Ti2AlC thin films belonging to the group of nanolaminate ternary compounds of composition Mn+1AXn. The required stoichiometry was achieved by means of alternating plasma pulses from three independent cathodes. We present x-ray diffraction and transmission electron microscopy analysis showing that epitaxial single phase growth of Ti2AlC has been achieved at a substrate temperature of 900 °C. Our results demonstrate a powerful method for MAX phase synthesis, allowing for phase tuning within the Mn+1AXn system.
Publisher: IOP Publishing
Date: 27-10-2011
Publisher: Elsevier BV
Date: 03-2021
Publisher: AIP Publishing
Date: 16-01-2014
DOI: 10.1063/1.4861179
Abstract: The early stages of InGaN/GaN quantum well growth for In-reduced conditions have been investigated for varying thickness and composition of the wells. The structures were studied by monochromated scanning transmission electron microscopy–valence electron energy loss spectroscopy spectrum imaging at high spatial resolution. It is found that beyond a critical well thickness and composition, quantum dots (width & nm) are formed inside the well. These are buried by compositionally graded InGaN, which is formed as GaN is grown while residual In is incorporated into the growing structure. It is proposed that these dots act as carrier localization centers inside the quantum wells.
Publisher: American Vacuum Society
Date: 10-02-2005
DOI: 10.1116/1.1861049
Abstract: We have synthesized Ta thin films on Si substrates placed along a wall of a 2-cm-deep and 1-cm-wide trench, using both a mostly neutral Ta flux by conventional dc magnetron sputtering (dcMS) and a mostly ionized Ta flux by high-power pulsed magnetron sputtering (HPPMS). Structure of the grown films was evaluated by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The Ta thin film grown by HPPMS has a smooth surface and a dense crystalline structure with grains oriented perpendicular to the substrate surface, whereas the film grown by dcMS exhibits a rough surface, pores between the grains, and an inclined columnar structure. The improved homogeneity achieved by HPPMS is a direct consequence of the high ion fraction of sputtered species.
Publisher: Elsevier BV
Date: 02-2007
Publisher: American Vacuum Society
Date: 07-11-2022
DOI: 10.1116/6.0002079
Abstract: InxGa1−x N is a strategically important material for electronic devices given its tunable bandgap, modulated by the In/Ga ratio. However, current applications are hindered by defects caused by strain relaxation and phase separation in the material. Here, we demonstrate growth of homogeneous InxGa1−x N films with 0.3 & x & 0.8 up to ∼30 nm using atomic layer deposition (ALD) with a supercycle approach, switching between InN and GaN deposition. The composition is uniform along and across the films, without signs of In segregation. The InxGa1−x N films show higher In-content than the value predicted by the supercycle model. A more pronounced reduction of GPCInN than GPCGaN during the growth processes of InN and GaN bilayers is concluded based on our analysis. The intermixing between InN and GaN bilayers is suggested to explain the enhanced overall In-content. Our results show the advantage of ALD to prepare high-quality InxGa1−x N films, particularly with high In-content, which is difficult to achieve with other growth methods.
Publisher: AIP Publishing
Date: 09-2021
DOI: 10.1063/5.0059078
Abstract: Mn+1AXn (MAX) phases' nanolaminated ternary carbides or nitrides possess a unique crystal structure in which single-atom-thick “A” sublayers are interleaved by alternative stacking of a “Mn+1Xn” sublayer these materials have been investigated as promising high-safety structural materials for industrial applications because of their laminated structure and metal and ceramic properties. However, limited of A-site elements in the definition of Mn+1AXn phases, it is a huge challenge for designing nanolaminated ferromagnetic materials with single-atom-thick two-dimensional iron layers occupying the A layers in the Mn+1AXn phases. Here, we report three new ternary magnetic Mn+1AXn phases (Ta2FeC, Ti2FeN, and Nb2FeC) with A sublayers of single-atom-thick two-dimensional iron through an isomorphous replacement reaction of Mn+1AXn precursors (Ta2AlC, Ti2AlN, and Nb2AlC) with a Lewis acid salts (FeCl2). All these Mn+1AXn phases exhibit ferromagnetic behavior. The Curie temperatures of the Ta2FeC and Nb2FeC Mn+1AXn phases are 281 and 291 K, respectively, i.e., close to room temperature. The saturation magnetization of these ternary magnetic MAX phases is almost two orders of magnitude higher than V2(Sn,Fe)C, whose A-site is partially substituted by Fe. Theoretical calculations on magnetic orderings of spin moments of Fe atoms in these nanolaminated magnetic Mn+1AXn phases reveal that the magnetism can be mainly ascribed to an intralayer exchange interaction of the two-dimensional Fe atomic layers. Owing to the richness in composition of Mn+1AXn phases, our work provides a large imaginary space for constructing functional single-atom-thick two-dimensional layers in materials using these nanolaminated templates.
Publisher: Elsevier BV
Date: 08-2018
Publisher: Springer Science and Business Media LLC
Date: 05-11-2018
DOI: 10.1038/S41598-018-34279-W
Abstract: Nanostructure formation via surface-diffusion-mediated segregation of ZrN and AlN in Zr 1−x Al x N films during high mobility growth conditions is investigated for 0 ≤ × ≤ 1. The large immiscibility combined with interfacial surface and strain energy balance resulted in a hard nanolabyrinthine lamellar structure with well-defined (semi) coherent c-ZrN and w-AlN domains of sub-nm to ~4 nm in 0.2 ≤ × ≤ 0.4 films, as controlled by atom mobility. For high AlN contents (x 0.49) Al-rich ZrN domains attain wurtzite structure within fine equiaxed nanocomposite wurtzite lattice. Slow diffusion in wurtzite films points towards crystal structure dependent driving force for decomposition. The findings of unlikelihood of iso-structural decomposition in c-Zr 1−x Al x N, and stability of w-Zr 1−x Al x N (in large × films) is complemented with first principles calculations.
Publisher: American Chemical Society (ACS)
Date: 07-06-2022
Publisher: American Chemical Society (ACS)
Date: 03-2019
DOI: 10.1021/JACS.9B00574
Abstract: Nanolaminated materials are important because of their exceptional properties and wide range of applications. Here, we demonstrate a general approach to synthesizing a series of Zn-based MAX phases and Cl-terminated MXenes originating from the replacement reaction between the MAX phase and the late transition-metal halides. The approach is a top-down route that enables the late transitional element atom (Zn in the present case) to occupy the A site in the pre-existing MAX phase structure. Using this replacement reaction between the Zn element from molten ZnCl
Publisher: American Vacuum Society
Date: 11-2005
DOI: 10.1116/1.2131081
Abstract: We have synthesized Ti–Si–C nanocomposite thin films by dc magnetron sputtering from a Ti3SiC2 compound target in an Ar discharge on Si(100), Al2O3(0001), and Al substrates at temperatures from room temperature to 300°C. Electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy showed that the films consisted of nanocrystalline (nc-) TiC and amorphous (a-) SiC, with the possible presence of a small amount of noncarbidic C. The growth mode was columnar, yielding a nodular film-surface morphology. Mechanically, the films exhibited a remarkable ductile behavior. Their nanoindentation hardness and E-modulus values were 20 and 290GPa, respectively. The electrical resistivity was 330μΩcm for optimal Ar pressure (4mTorr) and substrate temperature (300°C). The resulting nc-TiC∕a-SiC films performed well as electrical contact material. These films’ electrical-contact resistance against Ag was remarkably low, 6μΩ at a contact force of 800N compared to 3.2μΩ for Ag against Ag. The chemical stability of the nc-TiC∕a-SiC films was excellent, as shown by a Battelle flowing mixed corrosive-gas test, with no N, Cl, or S contaminants entering the bulk of the films.
Publisher: IOP Publishing
Date: 11-07-2012
DOI: 10.1088/0957-4484/23/30/305708
Abstract: Growing InGaN quantum dots (QDs) at the apex of hexagonal GaN pyramids is an elegant approach to achieve a deterministic positioning of QDs. Despite similar synthesis procedures by metal organic chemical vapor deposition, the optical properties of the QDs reported in the literature vary drastically. The QDs tend to exhibit either narrow or broad emission lines in the micro-photoluminescence spectra. By coupled microstructural and optical investigations, the QDs giving rise to narrow emission lines were concluded to nucleate in association with a (0001) facet at the apex of the GaN pyramid.
Publisher: American Chemical Society (ACS)
Date: 29-09-2020
Publisher: Elsevier BV
Date: 06-2006
Publisher: IOP Publishing
Date: 03-10-2017
Publisher: American Chemical Society (ACS)
Date: 03-07-2020
DOI: 10.26434/CHEMRXIV.12588479.V1
Abstract: The atomic structure and local composition of high quality epitaxial substoichiometric titaniumdiboride (TiB 1.9 ) thin film, deposited by unbalanced magnetron sputtering, were studied usinganalytical high-resolution scanning transmission electron microscopy, density functional theoryand image simulations. The unmatched Ti is pinpointed to planar defects on {1-100} prismaticplanes and attributed to the absence of B between Ti planes that locally relaxes the structure.This mechanism allows the line compound to accommodate the off-stoichiometry and remaina line compound between defects. The planar defects are embedded in otherwise stoichiometricTiB 2 and are delineated by insertion of dislocations. An accompanied decrease in Ti-Ti bondlengths along and across the faults is observed.Introduction
Publisher: Elsevier BV
Date: 08-2018
Publisher: American Chemical Society (ACS)
Date: 23-02-2022
Publisher: American Chemical Society (ACS)
Date: 27-07-2015
DOI: 10.1021/ACS.NANOLETT.5B00737
Abstract: The properties of two-dimensional (2D) materials depend strongly on the chemical and electrochemical activity of their surfaces. MXene, one of the most recent additions to 2D materials, shows great promise as an energy storage material. In the present investigation, the chemical and structural properties of in idual Ti3C2 MXene sheets with associated surface groups are investigated at the atomic level by aberration corrected STEM-EELS. The MXene sheets are shown to exhibit a nonuniform coverage of O-based surface groups which locally affect the chemistry. Additionally, native point defects which are proposed to affect the local surface chemistry, such as oxidized titanium adatoms (TiOx), are identified and found to be mobile.
Publisher: AIP Publishing
Date: 15-12-2011
DOI: 10.1063/1.3671560
Abstract: We study the effect of high power pulses in reactive magnetron sputter epitaxy on the structural properties of GaN (0001) thin films grown directly on Al2O3 (0001) substrates. The epilayers are grown by sputtering from a liquid Ga target, using a high power impulse magnetron sputtering power supply in a mixed N2/Ar discharge. X-ray diffraction, micro-Raman, micro-photoluminescence, and transmission electron microscopy investigations show the formation of two distinct types of domains. One almost fully relaxed domain exhibits superior structural and optical properties as evidenced by rocking curves with a full width at half maximum of 885 arc sec and a low temperature band edge luminescence at 3.47 eV with the full width at half maximum of 10 meV. The other domain exhibits a 14 times higher isotropic strain component, which is due to the higher densities of the point and extended defects, resulting from the ion bombardment during growth. Voids form at the domain boundaries. Mechanisms for the formation of differently strained domains, along with voids during the epitaxial growth of GaN are discussed.
Publisher: Elsevier BV
Date: 2021
Publisher: Wiley
Date: 18-04-2007
Publisher: The Electrochemical Society
Date: 2003
DOI: 10.1149/1.1556599
Publisher: Proceedings of the National Academy of Sciences
Date: 26-12-2019
Abstract: M n+1 AX n phases are a family of inherently nanolaminated ternary compounds with hexagonal crystal structure (space group P 63 /mmc , 194 ). Here, M is vanadium element, and A is Fe, Co, Ni, Mn, or their binary/ternary/quaternary mixtures. Due to the elemental flexibility at A site, 15 nanolaminated V 2 ( A x Sn 1-x )C MAX phases are synthesized, including 1 high-entropy MAX phase that all Fe, Co, Ni, Mn, and Sn elements simultaneously occupied A site. Tailoring of in idual single–atom-thick layers in nanolaminated MAX phases offers atomic-level control of material properties, such as their distinct magnetic behaviors. The alloying in 2-dimensional A layer of MAX phases provides a unique route to design their crystal structure and to discover unexploited properties, which would develop promising functional materials for microelectronic device.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2NA00456A
Abstract: We report single-rod photodetectors with high responsivity and gain based on indium aluminium nitride (In x Al 1− x N) nanorods (NRs). A transition from a positive photoresponse to a negative photoresponse was observed while increasing the In composition.
Publisher: IEEE
Date: 07-2008
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 12-2012
Publisher: MDPI AG
Date: 04-2021
DOI: 10.3390/MA14071739
Abstract: Several ternary phases are known in the Mo-Fe-B system. Previous ab initio calculations have predicted that they should exhibit a tempting mix of mechanical and magnetic properties. In this study, we have deposited Mo-Fe-B films with a Fe-content varying from 0–37 at.% using non-reactive DC (direct current) magnetron sputtering. The phase composition, microstructure, and mechanical properties were investigated using X-ray diffraction, scanning transmission electron microscopy, and nanoindentation measurements. Films deposited at 300 °C and with at.% Fe are nanocomposites consisting of two amorphous phases: a metal-rich phase and a metal-deficient phase. Hardness and elastic modulus were reduced with increasing Fe-content from ~29 to ~19 GPa and ~526 to ~353 GPa, respectively. These values result in H3/E2 ratios of 0.089–0.052 GPa, thereby indicating brittle behaviour of the films. Also, no indication of crystalline ternary phases was observed at temperatures up to 600 °C, suggesting that higher temperatures are required for such films to form.
Publisher: Springer Science and Business Media LLC
Date: 06-08-2021
DOI: 10.1038/S42003-021-02458-7
Abstract: Two challenges that the global wheat industry is facing are a lowering nitrogen-use efficiency (NUE) and an increase in the reporting of wheat-protein related health issues. Sulphur deficiencies in soil has also been reported as a global issue. The current study used large-scale field and glasshouse experiments to investigate the sulphur fertilization impacts on sulphur deficient soil. Here we show that sulphur addition increased NUE by more than 20% through regulating glutamine synthetase. Alleviating the soil sulphur deficiency highly significantly reduced the amount of gliadin proteins indicating that soil sulphur levels may be related to the biosynthesis of proteins involved in wheat-induced human pathologies. The sulphur-dependent wheat gluten biosynthesis network was studied using transcriptome analysis and amino acid metabolomic pathway studies. The study concluded that sulphur deficiency in modern farming systems is not only having a profound negative impact on productivity but is also impacting on population health.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6NR05168E
Abstract: Recent developments in fabrication techniques and extensive investigations of the physical properties of III-V semiconductor nanowires (NWs), such as GaAs NWs, have demonstrated their potential for a multitude of advanced electronic and photonics applications. Alloying of GaAs with nitrogen can further enhance the performance and extend the device functionality via intentional defects and heterostructure engineering in GaNAs and GaAs/GaNAs coaxial NWs. In this work, it is shown that incorporation of nitrogen in GaAs NWs leads to formation of three-dimensional confining potentials caused by short-range fluctuations in the nitrogen composition, which are superimposed on long-range alloy disorder. The resulting localized states exhibit a quantum-dot like electronic structure, forming optically active states in the GaNAs shell. By directly correlating the structural and optical properties of in idual NWs, it is also shown that formation of the localized states is efficient in pure zinc-blende wires and is further facilitated by structural polymorphism. The light emission from these localized states is found to be spectrally narrow (∼50-130 μeV) and is highly polarized (up to 100%) with the preferable polarization direction orthogonal to the NW axis, suggesting a preferential orientation of the localization potential. These properties of self-assembled nano-emitters embedded in the GaNAs-based nanowire structures may be attractive for potential optoelectronic applications.
Publisher: American Physical Society (APS)
Date: 19-04-2016
Publisher: American Physical Society (APS)
Date: 10-05-2013
Publisher: American Physical Society (APS)
Date: 14-11-2014
Publisher: IOP Publishing
Date: 09-02-2017
Abstract: We have examined the early stages of self-induced InAlN core-shell nanorod (NR) formation processes on amorphous carbon substrates in plan-view geometry by means of transmission electron microscopy methods. The results show that the grown structure phase separates during the initial moments of deposition into a majority of Al-rich InAlN and a minority of In-enriched InAlN islands. The islands possess polygonal shapes and are mainly oriented along a crystallographic c-axis. The growth proceeds with densification and coalescence of the In-enriched islands, resulting in a base for the In-enriched NR cores with shape transformation to hexagonal. The Al-rich shell formation around such early cores is observed at this stage. The matured core-shell structure grows axially and radially, eventually reaching a steady growth state which is dominated by the axial NR growth. We discuss the NR formation mechanism by considering the adatom surface kinetics, island surface energy, phase separation of InAlN alloys, and incoming flux directions during dual magnetron sputter epitaxy.
Publisher: Elsevier BV
Date: 12-2009
Publisher: AIP Publishing
Date: 22-06-2015
DOI: 10.1063/1.4922877
Abstract: A high mobility of 2250 cm2/V·s of a two-dimensional electron gas (2DEG) in a metalorganic chemical vapor deposition-grown AlGaN/GaN heterostructure was demonstrated. The mobility enhancement was a result of better electron confinement due to a sharp AlGaN/GaN interface, as confirmed by scanning transmission electron microscopy analysis, not owing to the formation of a traditional thin AlN exclusion layer. Moreover, we found that the electron mobility in the sharp-interface heterostructures can sustain above 2000 cm2/V·s for a wide range of 2DEG densities. Finally, it is promising that the sharp-interface AlGaN/GaN heterostructure would enable low contact resistance fabrication, less impurity-related scattering, and trapping than the AlGaN/AlN/GaN heterostructure, as the high-impurity-contained AlN is removed.
Publisher: Elsevier BV
Date: 12-2004
Publisher: Elsevier BV
Date: 02-2011
Publisher: Wiley
Date: 11-04-2005
Publisher: IOP Publishing
Date: 09-2023
Abstract: This study presents a novel approach to forming low-resistance ohmic contacts for AlGaN/GaN HEMTs. The optimized contacts exhibit an outstanding contact resistance of approximately 0.15 Ω·mm. This is achieved by firstly recessing the barrier of the heterostructure to a depth beyond the channel. In this way, the channel region is exposed on the sidewall of the recess. The coverage of the Ti/Al/Ti ohmic metalization on the sidewall is ensured through tilting of the s le during evaporation. The annealing process is performed at a low temperature of 550 °C. The approach does not require precise control of the recess etching. Furthermore, the method is directly applicable to most barrier designs in terms of thickness and Al-concentration. The impact of recessed sidewall angle, thickness and ratio of Ti and Al layers, and the annealing procedure are investigated. Structural and chemical analyses of the interface between the ohmic contacts and epi-structure indicate the formation of ohmic contacts by the extraction of nitrogen from the epi-structure. The approach is demonstrated on HEMT-structures with two different barrier designs in terms of Al-concentration and barrier thickness. The study demonstrate large process window in regard to recess depth and duration of the annealing as well as high uniformity of the contact resistance across the s les, rendering the approach highly suitable for industrial production processes.
Publisher: American Chemical Society (ACS)
Date: 31-03-2023
Publisher: Springer Science and Business Media LLC
Date: 15-07-2014
Publisher: American Chemical Society (ACS)
Date: 22-05-2015
DOI: 10.1021/ACS.NANOLETT.5B01054
Abstract: III-V semiconductor nanowires (NWs) have gained significant interest as building blocks in novel nanoscale devices. The one-dimensional (1D) nanostructure architecture allows one to extend band structure engineering beyond quantum confinement effects by utilizing formation of different crystal phases that are thermodynamically unfavorable in bulk materials. It is therefore of crucial importance to understand the influence of variations in the NWs crystal structure on their fundamental physical properties. In this work we investigate effects of structural polytypism on the optical properties of gallium phosphide and GaP/GaNP core/shell NW structures by a correlative investigation on the structural and optical properties of in idual NWs. The former is monitored by transmission electron microscopy, whereas the latter is studied via cathodoluminescence (CL) mapping. It is found that structural defects, such as rotational twins in zinc blende (ZB) GaNP, have detrimental effects on light emission intensity at low temperatures by promoting nonradiative recombination processes. On the other hand, formation of the wurtzite (WZ) phase does not notably affect the CL intensity neither in GaP nor in the GaNP alloy. This suggests that zone folding in WZ GaP does not enhance its radiative efficiency, consistent with theoretical predictions. We also show that the change in the lattice structure have negligible effects on the bandgap energies of the GaNP alloys, at least within the range of the investigated nitrogen compositions of <2%. Both WZ and ZB GaNP are found to have a significantly higher efficiency of radiative recombination as compared with that in parental GaP, promising for potential applications of GaNP NWs as efficient nanoscale light emitters within the desirable amber-red spectral range.
Publisher: Wiley
Date: 31-12-2021
Publisher: AIP Publishing
Date: 04-03-2002
DOI: 10.1063/1.1455698
Abstract: The nucleation and microstructure of large-scale columnar domains present in hydride vapor phase epitaxial (HPVE)-GaN layers grown directly on sapphire have been studied using cathodoluminescence and transmission electron microscopy. The domains are distributed in a quasicontinuous layer close to the GaN/sapphire interface. The domain boundaries are found to be associated with stacking mismatch defects. They are initiated at steps on the sapphire surface and are formed between nucleation islands growing on adjacent terraces. The formation of these domains in the initial stages of HVPE-GaN heteroepitaxial growth is proposed to play an important role in the strain relaxation mechanism.
Publisher: American Chemical Society (ACS)
Date: 11-10-2016
DOI: 10.1021/ACS.INORGCHEM.6B01398
Abstract: For the first time, MAX phases in the Hf-Al-C system were experimentally synthesized using reactive hot pressing. HfC was observed as the main competing phase. The lattice parameters of Hf
Publisher: Trans Tech Publications, Ltd.
Date: 03-2009
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.615-617.275
Abstract: We have performed 2D X-ray diffraction mapping of the SiC lattice basal plane orientation over full 2” SiC substrates. Measurements of the omega angle were made in two perpendicular directions -20 and -100 , which gives the complete vectorized tilt of the basal planes. The Mapping revealed two characteristic bending behaviors on measured commercial wafers. The first is characterized by large variations in omega angle across the wafer in both crystallographic directions. The continuously changing omega angle in both directions gives the wafer an apparent rotationally symmetric bending which is concave towards the growth direction. The second characteristic behavior is seen in wafers with lower degree of omega angle variation. The variations in this type of wafers are not changing linearly, but are bending the basal planes with two-fold symmetry.
Publisher: Springer Science and Business Media LLC
Date: 13-03-2020
DOI: 10.1038/S41467-020-15105-2
Abstract: The integration and cooperation of mechanoreceptors, neurons and synapses in somatosensory systems enable humans to efficiently sense and process tactile information. Inspired by biological somatosensory systems, we report an optoelectronic spiking afferent nerve with neural coding, perceptual learning and memorizing capabilities to mimic tactile sensing and processing. Our system senses pressure by MXene-based sensors, converts pressure information to light pulses by coupling light-emitting diodes to analog-to-digital circuits, then integrates light pulses using a synaptic photomemristor. With neural coding, our spiking nerve is capable of not only detecting simultaneous pressure inputs, but also recognizing Morse code, braille, and object movement. Furthermore, with dimensionality-reduced feature extraction and learning, our system can recognize and memorize handwritten alphabets and words, providing a promising approach towards e-skin, neurorobotics and human-machine interaction technologies.
Publisher: Springer Science and Business Media LLC
Date: 29-01-2013
Publisher: Elsevier BV
Date: 02-2016
Publisher: Elsevier BV
Date: 10-2021
Publisher: Wiley
Date: 22-11-2017
Publisher: Informa UK Limited
Date: 08-03-2022
Publisher: Elsevier BV
Date: 2008
Publisher: Elsevier BV
Date: 08-2021
Publisher: American Physical Society (APS)
Date: 24-01-2022
Publisher: Wiley
Date: 04-2018
Abstract: The exploration of 2D solids is one of our time's generators of materials discoveries. A recent addition to the 2D world is MXenes that possses a rich chemistry due to the large parent family of MAX phases. Recently, a new type of atomic laminated phases (coined i-MAX) is reported, in which two different transition metal atoms are ordered in the basal planes. Herein, these i-MAX phases are used in a new route for tailoriong the MXene structure and composition. By employing different etching protocols to the parent i-MAX phase (Mo
Publisher: AIP Publishing
Date: 17-08-2009
DOI: 10.1063/1.3211124
Abstract: Highly oriented ZnO nanotubes were fabricated on a silicon substrate by aqueous chemical growth at low temperature (& °C) by trimming of ZnO nanorods. The yield of nanotubes in the s le was 100%. Photoluminescence spectroscopy of the nanotubes reveals an enhanced and broadened ultraviolet (UV) emission peak, compared with the initial nanorods. This effect is attributed to whispering gallery mode resonance. In addition, a redshift of the UV emission peak is also observed. Enhancement in the deep defect band emission in the nanotubes compared to nanorods was also manifested as a result of the increased surface area.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 17-03-2023
Abstract: Intercalated layered materials offer distinctive properties and serve as precursors for important two-dimensional (2D) materials. However, intercalation of non–van der Waals structures, which can expand the family of 2D materials, is difficult. We report a structural editing protocol for layered carbides (MAX phases) and their 2D derivatives (MXenes). Gap-opening and species-intercalating stages were respectively mediated by chemical scissors and intercalants, which created a large family of MAX phases with unconventional elements and structures, as well as MXenes with versatile terminals. The removal of terminals in MXenes with metal scissors and then the stitching of 2D carbide nanosheets with atom intercalation leads to the reconstruction of MAX phases and a family of metal-intercalated 2D carbides, both of which may drive advances in fields ranging from energy to printed electronics.
Publisher: IOP Publishing
Date: 20-11-2014
DOI: 10.1088/0957-4484/25/49/495702
Abstract: Indium segregation in a narrow InGaN single quantum well creates quantum dot (QD) like exciton localization centers. Cross-section transmission electron microscopy reveals varying shapes and lateral sizes in the range ∼1-5 nm of the QD-like features, while scanning near field optical microscopy demonstrates a highly inhomogeneous spatial distribution of optically active in idual localization centers. Microphotoluminescence spectroscopy confirms the spectrally inhomogeneous distribution of localization centers, in which the exciton and the biexciton related emissions from single centers of varying geometry could be identified by means of excitation power dependencies. Interestingly, the biexciton binding energy (E(b)xx) was found to vary from center to center, between 3 to -22 meV, in correlation with the exciton emission energy. Negative binding energies are only justified by a three-dimensional quantum confinement, which confirms QD-like properties of the localization centers. The observed energy correlation is proposed to be understood as variations of the lateral extension of the confinement potential, which would yield smaller values of E(b)xx for reduced lateral extension and higher exciton emission energy. The proposed relation between lateral extension and E(b)xx is further supported by the exciton and the biexciton recombination lifetimes of a single QD, which suggest a lateral extension of merely ∼3 nm for a QD with strongly negative E(b)xx = -15.5 meV.
Publisher: MDPI AG
Date: 07-04-2018
DOI: 10.3390/NANO8040223
Abstract: GaN nanorods, essentially free from crystal defects and exhibiting very sharp band-edge luminescence, have been grown by reactive direct-current magnetron sputter epitaxy onto Si (111) substrates at a low working pressure of 5 mTorr. Upon diluting the reactive N2 working gas with a small amount of Ar (0.5 mTorr), we observed an increase in the nanorod aspect ratio from 8 to ~35, a decrease in the average diameter from 74 to 35 nm, and a two-fold increase in nanorod density. With further dilution (Ar = 2.5 mTorr), the aspect ratio decreased to 14, while the diameter increased to 60 nm and the nanorod density increased to a maximum of 2.4 × 109 cm−2. Yet, lower N2 partial pressures eventually led to the growth of continuous GaN films. The observed morphological dependence on N2 partial pressure is explained by a change from N-rich to Ga-rich growth conditions, combined with reduced GaN-poisoning of the Ga-target as the N2 gas pressure is reduced. Nanorods grown at 2.5 mTorr N2 partial pressure exhibited a high intensity 4 K photoluminescence neutral donor bound exciton transitions (D0XA) peak at ~3.479 eV with a full-width-at-half-maximum of 1.7 meV. High-resolution transmission electron microscopy corroborated the excellent crystalline quality of the nanorods.
Publisher: Springer Science and Business Media LLC
Date: 13-04-2020
Publisher: AIP Publishing
Date: 15-12-2006
DOI: 10.1063/1.2402971
Abstract: Epitaxial domain formation and textured growth in AlN thin films deposited on Si(001) substrates by reactive magnetron sputtering was studied by transmission electron microscopy and x-ray diffraction. The films have a wurtzite type structure with a crystallographic orientation relationship to the silicon substrate of AlN(0001)‖Si(001). The AlN film is observed to nucleate randomly on the Si surface and grows three dimensionally, forming columnar domains. The in-plane orientation reveals four domains with their a axes rotated by 15° with respect to each other: AlN⟨112¯0⟩‖Si[110], AlN⟨011¯0⟩‖Si[110], AlN⟨112¯0⟩‖Si[100], and AlN⟨011¯0⟩‖Si[100] An explanation of the growth mode based on the large lattice mismatch and the topology of the substrate surface is proposed.
Publisher: Wiley
Date: 27-10-2016
Abstract: Ladder-type "torsion-free" conducting polymers (e.g., polybenzimidazobenzophenanthroline (BBL)) can outperform "structurally distorted" donor-acceptor polymers (e.g., P(NDI2OD-T2)), in terms of conductivity and thermoelectric power factor. The polaron delocalization length is larger in BBL than in P(NDI2OD-T2), resulting in a higher measured polaron mobility. Structure-function relationships are drawn, setting material-design guidelines for the next generation of conducting thermoelectric polymers.
Publisher: Elsevier BV
Date: 03-2022
Publisher: Springer International Publishing
Date: 2019
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/CP18273
Abstract: The wheat NAM-B1 and NAM-A1 genes are positively associated with grain protein content (GPC) in wheat. We conducted molecular characterisation of the NAM-1 genes in 51 Australian wheat varieties (Triticum aestivum L.), with the aim of improving GPC and nitrogen-usage efficiency in Australian wheat. In summary, the wild type NAM-B1 gene, which originated from Israel, was identified in two Australian wheat varieties. Five varieties contained a deletion allele, whereas the majority (43) harboured a non-functional NAM-B1 allele and one variety contained both functional and non-functional alleles. Twenty-six Australian wheat varieties contained the NAM-A1a haplotype, which was similar to its well-characterised homoeolog NAM-B1 wild type and associated with high GPC. The NAM-D1 gene in the 51 wheat varieties was also characterised, and no gene variation in the exon regions was noted only two single-nucleotide polymorphisms in introns 1 and 2 were found among the 51 varieties.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1NA00642H
Abstract: Felxiable Mo 1.33 C i -MXene/MoS 2 /graphene (MOMG) nanocomposite electrode delivers volumetric capacitance up to 1600 F cm −3 in sulphric acid electolyte.
Publisher: Elsevier BV
Date: 08-2007
Publisher: AIP Publishing
Date: 04-04-2011
DOI: 10.1063/1.3576912
Abstract: Electronic-grade GaN (0001) epilayers have been grown directly on Al2O3 (0001) substrates by reactive direct-current-magnetron sputter epitaxy (MSE) using a liquid Ga sputtering target in an Ar/N2 atmosphere. The as-grown GaN epitaxial films exhibit low threading dislocation density on the order of ≤1010 cm−2 determined by transmission electron microscopy and modified Williamson–Hall plot. X-ray rocking curve shows narrow full-width at half maximum (FWHM) of 1054 arc sec of the 0002 reflection. A sharp 4 K photoluminescence peak at 3.474 eV with a FWHM of 6.3 meV is attributed to intrinsic GaN band edge emission. The high structural and optical qualities indicate that MSE-grown GaN epilayers can be used for fabricating high-performance devices without the need of any buffer layer.
Publisher: Elsevier BV
Date: 11-2013
Publisher: Springer Science and Business Media LLC
Date: 03-07-2007
Publisher: Elsevier BV
Date: 04-2002
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2018
Publisher: Springer Science and Business Media LLC
Date: 22-07-2021
DOI: 10.1007/S40820-021-00684-6
Abstract: MAX phases are gaining attention as precursors of two-dimensional MXenes that are intensively pursued in applications for electrochemical energy storage. Here, we report the preparation of V 2 SnC MAX phase by the molten salt method. V 2 SnC is investigated as a lithium storage anode, showing a high gravimetric capacity of 490 mAh g −1 and volumetric capacity of 570 mAh cm −3 as well as superior rate performance of 95 mAh g −1 (110 mAh cm −3 ) at 50 C, surpassing the ever-reported performance of MAX phase anodes. Supported by operando X-ray diffraction and density functional theory, a charge storage mechanism with dual redox reaction is proposed with a Sn–Li (de)alloying reaction that occurs at the edge sites of V 2 SnC particles where Sn atoms are exposed to the electrolyte followed by a redox reaction that occurs at V 2 C layers with Li. This study offers promise of using MAX phases with M-site and A-site elements that are redox active as high-rate lithium storage materials.
Publisher: Elsevier BV
Date: 10-2016
Publisher: American Physical Society (APS)
Date: 10-2004
Publisher: American Chemical Society (ACS)
Date: 05-2018
Abstract: All known materials wear under extended mechanical contacting. Superlubricity may present solutions, but is an expressed mystery in C-based materials. We report negative wear of carbon nitride films a wear-less condition with mechanically induced material inflation at the nanoscale and friction coefficient approaching ultralow values (0.06). Superlubricity in carbon nitride is expressed as C-N bond breaking for reduced coupling between graphitic-like sheets and eventual N
Publisher: Elsevier BV
Date: 06-2019
Publisher: Elsevier BV
Date: 07-2016
Publisher: Wiley
Date: 06-2017
Publisher: Informa UK Limited
Date: 10-2019
Publisher: Elsevier BV
Date: 04-2019
Publisher: Springer Science and Business Media LLC
Date: 06-02-2018
DOI: 10.1038/S41598-018-20935-8
Abstract: Wheat ( Triticum aestivum ) quality is mainly determined by grain storage protein compositions. Sulphur availability is essential for the biosynthesis of the main wheat storage proteins. In this study, the impact of different sulphur fertilizer regimes on a range of agronomically important traits and associated gene networks was studied. High-performance liquid chromatography was used to analyse the protein compositions of grains grown under four different sulphur treatments. Results revealed that sulphur supplementation had a significant effect on grain yield, harvest index, and storage protein compositions. Consequently, two comparative sulphur fertilizer treatments (0 and 30 kg ha −1 sulphur, with 50 kg ha −1 nitrogen) at seven days post-anthesis were selected for a transcriptomics analysis to screen for differentially expressed genes (DEGs) involved in the regulation of sulphur metabolic pathways. The International Wheat Genome Sequencing Consortium chromosome survey sequence was used as reference. Higher sulphur supply led to one up-regulated DEG and sixty-three down-regulated DEGs. Gene ontology enrichment showed that four down-regulated DEGs were significantly enriched in nitrogen metabolic pathway related annotation, three of which were annotated as glutamine synthetase. The Kyoto Encyclopedia of Genes and Genomes pathway enrichment identified three significantly enriched pathways involved in nitrogen and amino acid metabolism.
Publisher: Elsevier BV
Date: 09-2020
Publisher: AIP Publishing
Date: 08-06-2015
DOI: 10.1063/1.4922301
Abstract: The effect of Mg doping on the microstructure of InN epitaxial films in relation to their free-charge carrier properties has been investigated by transmission electron microscopy (TEM) and aberration corrected scanning TEM. We observe a direct correlation between Mg concentration and the formation of stacking faults. The threading dislocation density is found to be independent of Mg concentration. The critical Mg concentration for the on-set of stacking faults formation is determined and found to correlate with the switch from p- to n-type conductivity in InN. Potential mechanisms involving stacking faults and point defect complexes are invoked in order to explain the observed conductivity reversal. Finally, the stacking faults are structurally determined and their role in the reduction of the free electron mobility in highly doped InN:Mg is discussed.
Publisher: Elsevier BV
Date: 07-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0NR07045A
Abstract: Tailored synthesis method is used to produce higher yield of (Mo 2/3 Y 1/3 ) 2 AlC i -MAX, for realization of 2D Mo 1.33 CT z MXene with ordered vacancies, the latter shows electrochemical performance equivalent to that produced from the Sc containing i -MAX.
Publisher: AIP Publishing
Date: 10-04-2023
DOI: 10.1063/5.0141517
Abstract: Compositionally graded channel AlGaN/GaN high electron mobility transistors (HEMTs) offer a promising route to improve device linearity, which is necessary for low-noise radio-frequency lifiers. In this work, we demonstrate different grading profiles of a 10-nm-thick AlxGa1−xN channel from x = 0 to x = 0.1 using hot-wall metal-organic chemical vapor deposition (MOCVD). The growth process is developed by optimizing the channel grading and the channel-to-barrier transition. For this purpose, the Al-profiles and the interface sharpness, as determined from scanning transmission electron microscopy combined with energy-dispersive x-ray spectroscopy, are correlated with specific MOCVD process parameters. The results are linked to the channel properties (electron density, electron mobility, and sheet resistance) obtained by contactless Hall and terahertz optical Hall effect measurements coupled with simulations from solving self-consistently Poisson and Schrödinger equations. The impact of incorporating a thin AlN interlayer between the graded channel and the barrier layer on the HEMT properties is investigated and discussed. The optimized graded channel HEMT structure is found to have similarly high electron density (∼ 9 × 10 12 cm−2) as the non-graded conventional structure, though the mobility drops from ∼ 2360 cm2/V s in the conventional to ∼ 960 cm2/V s in the graded structure. The transconductance gm of the linearly graded channel HEMTs is shown to be flatter with smaller g m ′ and g m ″ as compared to the conventional non-graded channel HEMT implying improved device linearity.
Publisher: Elsevier BV
Date: 10-2014
Publisher: Elsevier BV
Date: 11-2015
Publisher: Elsevier BV
Date: 10-2016
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NA00324J
Abstract: MXenes are an extensive family of 2D transition metal carbides and nitrides, whose properties are strongly affected by surface terminations, typically O and F. Herein, we enable chlorine as a new termination, thereby expanding the property space.
Publisher: AIP Publishing
Date: 15-08-2010
DOI: 10.1063/1.3467521
Abstract: Periodic precipitation patterns in C:Ni nanocomposites grown by energetic ion codeposition are investigated. Films were grown at room temperature by ionized physical vapor deposition using a pulsed filtered cathodic vacuum arc. We reveal the role of the film composition, ion energy and incidence angle on the film morphology using transmission electron microscopy and grazing incidence small angle x-ray scattering. Under these growth conditions, phase separation occurs in a thin surface layer which has a high atomic mobility due to energetic ion impacts. This layer is an advancing reaction front, which switches to an oscillatory mode, producing periodic precipitation patterns. Our results show that the ion induced atomic mobility is not random, as it would be in the case of thermal diffusion but conserves to a large extent the initial direction of the incoming ions. This results in a tilted pattern under oblique ion incidence. A dependence of the nanopattern periodicity and tilt on the growth parameters is established and pattern morphology control via ion velocity is demonstrated.
Publisher: Elsevier BV
Date: 11-2014
Publisher: Elsevier BV
Date: 03-2021
Publisher: AIP Publishing
Date: 22-04-2013
DOI: 10.1063/1.4802758
Abstract: Using in situ transmission electron microscopy, we investigated the kinetics of liquid Ga droplet decay on thin amorphous carbon films during annealing at 773 K. The transmission electron microscopy images reveal that liquid Ga forms spherical droplets and undergo coarsening/decay with increasing time. We find that the droplet volumes change non-linearly with time and the volume decay rates depend on their local environment. By comparing the late-stage decay behavior of the droplets with the classical mean-field theory model for Ostwald ripening, we determine that the decay of Ga droplets occurs in the surface diffusion limited regime.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Elsevier BV
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 05-10-2017
DOI: 10.1038/S41598-017-12702-Y
Abstract: Selective-area growth (SAG) of single-crystal wurtzite GaN nanorods (NRs) directly onto Si(001) substrates with un-etched native SiO x amorphous layer, assisted by a patterning TiN x mask fabricated by nanosphere lithography (NSL), has been realized by reactive magnetron sputter epitaxy (MSE). The GaN NRs were grown vertically to the substrate surface with the growth direction along c -axis in the well-defined nano-opening areas. A 5-step structural and morphological evolution of the SAG NRs observed at different sputtering times depicts a comprehensive growth model, listed in sequence as: formation of a polycrystalline wetting layer, predominating c -axis oriented nucleation, coarsening and coalescence of multi-islands, single NR evolution, and finally quasi-equilibrium crystal shape formation. Room-temperature cathodoluminescence spectroscopy shows a strong GaN bandedge emission with a uniform luminescence across the NRs, indicating that the SAG NRs are grown with high quality and purity. In addition, single-longitudinal-mode lasing, attributed to well-faceted NR geometry forming a Fabry–Pérot cavity, was achieved by optical pumping, paving a way for fabricating high-performance laser optoelectronics using MSE.
Publisher: AIP Publishing
Date: 10-2008
DOI: 10.1063/1.2959835
Abstract: Ti/C and TiC/C multilayers with periods ranging from 2 to 18 nm were grown by filtered high current pulsed cathodic arc. The growth was monitored in situ by ellipsometry and cantilever stress measurements. The ellipsometry results reveal that the optical properties of the carbon vary as a function of thickness. Correspondingly, the stress in each carbon layer as measured in situ exhibits two well defined values: initially the stress is low and then takes on a higher value for the remainder of the layer. Transmission electron microscopy shows that the initial growth of carbon on Ti or TiC layer is oriented with graphitic basal planes aligned parallel to the interface. After 2–4 nm of growth, the graphitic structure transforms to amorphous carbon. Electron energy loss spectroscopy shows that the carbon layer simultaneously undergoes a transition from sp2 rich to sp3 rich material.
Publisher: Springer Science and Business Media LLC
Date: 12-12-2022
DOI: 10.1007/S12274-021-3913-Y
Abstract: Electrochromic (EC) materials that change color with voltage have been widely studied for use in dynamic windows. However, colorless-to-colorful switching with high contrast ratio is generically unattainable, especially for colorless-to-black electrochromic materials with an ultrahigh contrast ratio over the entire visible region. In this work, we developed Nb 1.33 C MXene-based dynamic windows with colorless-to-black switching of up to 75% reversible change in transmittance from 300 to 1,500 nm. By exploring the electrochromic effects of different electrolytes through in situ optical changes and electrochemical quartz crystal microbalance (EQCM), it is found that electrochromic behavior is greatly influenced by the extent of reversible Li + insertion/deinsertion between the two-dimensional Nb 1.33 C MXene nanosheets. In addition, a colorless-to-black EC device based on Nb 1.33 C with an overall integrated contrast ratio over 80% was successfully constructed by a solution-processable spin coating method. This work enables a simple route to fabricate MXene-based high-performance electrochromic smart windows, which is important for further expanding the application of MXenes to optoelectronic and photonic applications.
Publisher: Elsevier BV
Date: 07-2022
Publisher: Wiley
Date: 07-04-2014
Publisher: AIP Publishing
Date: 15-12-2001
DOI: 10.1063/1.1415363
Abstract: Thick hydride vapor phase epitaxial GaN layers are grown on metalorganic chemical vapor deposited GaN template layers as well as directly on sapphire, with the aim of investigating the effect of the template on the strain relaxation and spatial distribution of free carriers in the overgrown GaN films. Spatially resolved cross-sectional micro-Raman spectroscopy, cathodoluminescence, and transmission electron microscopy show improved crystalline quality for growth on metalorganic chemical vapor deposited GaN templates. The highly doped and highly defective near-substrate layer composed of columnar domains, typically present in hydride vapor phase epitaxial GaN films grown directly on sapphire, is absent in the layers grown on templates. Consequently, this results in elimination of the nonuniformities of free electron distribution, a lower residual free carrier concentration (& cm−3), and improved strain relaxation.
Publisher: Elsevier BV
Date: 08-2015
Publisher: MDPI AG
Date: 16-07-2020
DOI: 10.3390/MOLECULES25143237
Abstract: Soybean-based food products are a major source of protein. In the present study, proteins in soybean milk from seeds of the cultivar Bunya (Glycine max) were extracted using the cheesecloth and the centrifuge methods. The milk was produced through mechanical crushing of both whole and split seeds in water. Following separation by either the cheesecloth or centrifuge, proteins were isolated from the soybean milk by using thiourea/urea solubilisation and then separated them using two-dimensional polyacrylamide gel electrophoresis. The isolated proteins were identified by mass spectrometry. A total of 97 spots were identified including 49 that displayed different abundances. Of the two separation techniques, centrifuge separation gave higher protein extraction and more intense protein spots than cheesecloth separation. Eleven of the β-subunits of β-conglycinin, three of the α-subunits of β-conglycinin, and four of the mutant glycinin showed different levels of abundances between separation techniques, which might be related to subsequent cheese quality. Notably, split-seed soybean milk has less allergenic proteins with four α-subunits of β-conglycinin compared to whole-seed milk with eight of those proteins. The sensory evaluation showed that the cheese produced from split-soybean milk received higher consumer preferences compared to that of whole seed, which could be explained by their proteomic differences. The demonstrated reference map for whole and split-seed soybean milk could be further utilized in the research related to soybean cheesemaking.
Publisher: AIP Publishing
Date: 15-09-2009
DOI: 10.1063/1.3208065
Abstract: Ternary Ti–Al–N films were deposited onto Al2O3 (0001) substrates by reactive cosputtering from elemental Ti and Al targets and analyzed by in situ and ex situ x-ray scattering, Rutherford backscattering spectroscopy, transmission electron microscopy, and x-ray photoemission spectroscopy. The deposition parameters were set to values that yield Ti:Al:N ratios of 2:1:1 and 4:1:3 at room temperature. 2TiAlN depositions at 675 °C result in epitaxial Ti2AlN growth with basal planes parallel to the substrate surface. Nominal 4TiAl3N depositions at 675 °C and above, however, yield domain growth of TiN and Ti2AlN due to Al loss to the vacuum. Depositions at a lower temperature of 600 °C yield films with correct 4:1:3 stoichiometry, but Ti4AlN3 formation is prevented, supposedly by insufficient adatom mobility. Instead, an incoherent Tin+1AlNn structure with random twinned stacking sequences n is obtained that exhibits both basal plane orientations parallel and nearly perpendicular to the substrate interface. X-ray photoemission spectroscopy shows that in contrast to stoichiometric nitrides the Al is metallically bonded and hence acts as twinning plane within the Tin+1AlNn stackings. Domains with perpendicular basal plane orientation overgrow those with parallel orientation in a competitive growth mode. The resulting morphology is a combination of smooth-surface parallel-basal-plane-oriented domains interrupted by repeated facetted hillocklike features with perpendicular basal plane orientation.
Publisher: Elsevier BV
Date: 06-2006
Publisher: Wiley
Date: 06-04-2018
Abstract: Structural design on the atomic level can provide novel chemistries of hybrid MAX phases and their MXenes. Herein, density functional theory is used to predict phase stability of quaternary i-MAX phases with in-plane chemical order and a general chemistry (W
Publisher: Elsevier BV
Date: 07-2005
Publisher: AIP Publishing
Date: 15-06-2010
DOI: 10.1063/1.3448235
Abstract: AlN(0001) was alloyed with ScN with molar fractions up to ∼22%, while retaining a single-crystal wurtzite (w-) structure and with lattice parameters matching calculated values. Material synthesis was realized by magnetron sputter epitaxy of thin films starting from optimal conditions for the formation of w-AlN onto lattice-matched w-AlN seed layers on Al2O3(0001) and MgO(111) substrates. Films with ScN contents between 23% and ∼50% exhibit phase separation into nanocrystalline ScN and AlN, while ScN-rich growth conditions yield a transformation to rocksalt structure Sc1−xAlxN(111) films. The experimental results are analyzed with ion beam analysis, x-ray diffraction, and transmission electron microscopy, together with ab initio calculations of mixing enthalpies and lattice parameters of solid solutions in wurtzite, rocksalt, and layered hexagonal phases.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8NR01986J
Abstract: We investigated the presence of adsorbed species on Nb 2 C MXene surfaces and their influence on the structural stability over time.
Publisher: Elsevier BV
Date: 05-2009
No related grants have been discovered for Per Persson.