ORCID Profile
0000-0002-2676-4856
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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: American Chemical Society (ACS)
Date: 19-01-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3NR00839H
Abstract: The first report of sub-4 nm mapping of donor : acceptor nanoparticle composition in eco-friendly colloidal dispersions for organic electronics.
Publisher: Elsevier BV
Date: 03-2021
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: 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: 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: American Chemical Society (ACS)
Date: 29-09-2020
Publisher: Wiley
Date: 18-02-2020
Publisher: IOP Publishing
Date: 03-10-2017
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: 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: 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: 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: IOP Publishing
Date: 20-02-2019
Publisher: American Chemical Society (ACS)
Date: 23-02-2022
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: 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: 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: 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.
No related grants have been discovered for Ingemar Persson.