ORCID Profile
0000-0002-2751-6109
Current Organisation
Monash University
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Publisher: AIP Publishing
Date: 12-11-2018
DOI: 10.1063/1.5063538
Abstract: We epitaxially grew 7 mol. % Nd-doped BaSnO3 (NBSO) thin films on double-side polished SrTiO3 (001) single-crystal substrates and optimized the oxygen pressure (PO2), substrate temperature (TS), and film thickness (t) to achieve excellent structural, optical, and electrical performance. By keeping TS (=800 °C) constant, NBSO films prepared at PO2 = 10 Pa show the best crystallization, yielding a full-width at half-maximum (FWHM) of the x-ray diffraction rocking curve of 0.079° and exhibiting a room-temperature resistivity (ρ) of ∼1.85 mΩ cm and a volume carrier density (n) of ∼8.5 × 1020/cm3. By keeping PO2 (=10 Pa) constant, the room-temperature ρ of NBSO films could be reduced to as low as 0.5 mΩ cm by increasing TS from 700 to 825° meanwhile, the volume carrier density and mobility show the maximum of 5.04 × 1020/cm3 and 24.9 cm2/Vs, respectively, for TS = 825 °C. For all as-grown NBSO thin films, the optical transmittance in the visible wavelength region is larger than 80%. The optimized comprehensive properties of the NBSO films with FWHM = 0.11°, ρ = 0.5 mΩ cm, μ = 24.9 cm2/Vs, and T & 80% are superior to those of other rare-earth and 4d- and 5d-transition metal-doped BaSnO3 thin films.
Publisher: American Physical Society (APS)
Date: 15-06-2023
Publisher: IOP Publishing
Date: 31-03-2023
Abstract: We report the synthesis of transition-metal-doped ferromagnetic elemental single-crystal semiconductors with quantum oscillations using the physical vapor transport method. The 7.7 atom% Cr-doped Te crystals (Cr:Te) show ferromagnetism, butterfly-like negative magnetoresistance in the low temperature ( .8 K) and low field ( .15 T) region, and high Hall mobility, e.g. 1320 cm 2 V −1 s −1 at 30 K and 350 cm 2 V −1 s −1 at 300 K, implying that Cr:Te crystals are ferromagnetic elemental semiconductors. When B // [001] // I, the maximum negative MR is ∼−27% at T = 20 K and B = 8 T. In the low temperature semiconducting region, Cr:Te crystals show strong discrete scale invariance dominated logarithmic quantum oscillations when the direction of the magnetic field B is parallel to the [100] crystallographic direction ( B // [100]) and show Landau quantization dominated Shubnikov-de Haas oscillations for B // [210] direction, which suggests the broken rotation symmetry of the Fermi pockets in the Cr:Te crystals. The findings of coexistence of multiple quantum oscillations and ferromagnetism in such an elemental quantum material may inspire more study of narrow bandgap semiconductors with ferromagnetism and quantum phenomena.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1TC01034D
Abstract: The topological nature of electronic states in HoSb significantly depends on spin orderings (NM, AFM or FM spin configuration). Only the electronic band structure in HoSb's antiferromagnetic state is confirmed to be topologically nontrivial.
Publisher: American Chemical Society (ACS)
Date: 06-02-2019
Abstract: Single-phase (00 l)-oriented Bi
Publisher: American Physical Society (APS)
Date: 30-08-2021
Publisher: Springer Science and Business Media LLC
Date: 27-05-2021
DOI: 10.1038/S41535-021-00354-1
Abstract: Linear magnetoresistance (LMR) is a special case of a magnetic-field induced resistivity response, which has been reported in highly disordered semiconductor systems and in topological materials. In this work, we observe LMR effect in half-metallic perovskite Sr 2 CrMoO 6 thin films, of which the maximum MR value exceeds +1600% at 2 K and 14 T. It is an unusual behavior in ferrimagnetic double perovskite material like Sr 2 CrMoO 6 , which are known for intrinsic tunneling-type negative magnetoresistance. In the thin films, the high carriers’ density (~10 22 cm −3 ) and ultrahigh mobility (~10 4 cm 2 V −1 s −1 ) provide a low-resistivity (~10 nΩ·cm) platform for spin-polarized current. Our DFT calculations and magnetic measurements further support the half-metal band structure. The LMR effect in Sr 2 CrMoO 6 could possibly originate from transport behavior that is governed by the guiding center motion of cyclotron orbitals, where the magnetic domain structure possibly provides disordered potential. The ultrahigh mobility and LMR in this system could broaden the applications of perovskites, and introduce more research on metallic oxide ferri-/ferro-magnetic materials.
Publisher: Elsevier BV
Date: 10-2019
Publisher: American Physical Society (APS)
Date: 21-09-2022
Publisher: MDPI AG
Date: 20-02-2023
DOI: 10.3390/MA16041736
Abstract: High-quality NdCrSb3 single crystals are grown using a Sn-flux method, for electronic transport and magnetic structure study. Ferromagnetic ordering of the Nd3+ and Cr3+ magnetic sublattices are observed at different temperatures and along different crystallographic axes. Due to the Dzyaloshinskii–Moriya interaction between the two magnetic sublattices, the Cr moments rotate from the b axis to the a axis upon cooling, resulting in a spin reorientation (SR) transition. The SR transition is reflected by the temperature-dependent magnetization curves, e.g., the Cr moments rotate from the b axis to the a axis with cooling from 20 to 9 K, leading to a decrease in the b-axis magnetization f and an increase in the a-axis magnetization. Our elastic neutron scattering along the a axis shows decreasing intensity of magnetic (300) peak upon cooling from 20 K, supporting the SR transition. Although the magnetization of two magnetic sublattices favours different crystallographic axes and shows significant anisotropy in magnetic and transport behaviours, their moments are all aligned to the field direction at sufficiently large fields (30 T). Moreover, the magnetic structure within the SR transition region is relatively fragile, which results in negative magnetoresistance by applying magnetic fields along either a or b axis. The metallic NdCrSb3 single crystal with two ferromagnetic sublattices is an ideal system to study the magnetic interactions, as well as their influences on the electronic transport properties.
Publisher: Informa UK Limited
Date: 20-04-2022
Publisher: American Vacuum Society
Date: 06-04-2022
DOI: 10.1116/6.0001771
Abstract: Good specimen quality is a key factor in achieving successful scanning transmission electron microscope analysis. Thin and damage-free specimens are prerequisites for obtaining atomic-resolution imaging. Topological insulator single crystals and thin films in the chalcogenide family such as Sb2Te3 are sensitive to electron and ion beams. It is, therefore, challenging to prepare a lamella suitable for high-resolution imaging from these topological insulator materials using standard focused ion-beam instruments. We have developed a modified method to fabricate thin focused ion-beam (FIB) lamellae with minimal ion-beam damage and artifacts. The technique described in the current study enables the reliable preparation of high-quality transmission electron microscope (TEM) specimens necessary for studying ultra-thin surface regions. We have successfully demonstrated that the careful selection of FIB milling parameters at each stage minimizes the damage layer without the need for post-treatment.
Publisher: American Physical Society (APS)
Date: 11-05-2022
Publisher: American Chemical Society (ACS)
Date: 02-12-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1TC02065J
Abstract: A novel ferromagnetic spinel CuCo 2 S 4 T c ∼ 125 K was discovered. The ferromagnetism originates from Co and Cu atoms, and leads to a positive magnetoresistance in the paramagnetic regime, and a cross-over in the ferromagnetic regime.
Publisher: American Chemical Society (ACS)
Date: 22-04-2019
Abstract: Fluorine-doped Fe(Se, Te) has been successfully synthesized using the melting method. A dual-oscillation effect was found in the F-doped s le, which combined both microstructural oscillation and chemical compositional oscillation. The microstructural oscillation could be attributed to alternate growth of tetragonal β-Fe(Se, Te) and hexagonal δ-Fe(Se, Te), which formed a pearlite-like structure and led to the enhancement of δ l flux pinning due to the alternating distributed nonsuperconducting δ-Fe(Se, Te) phase. The chemical compositional oscillations in β-Fe(Se, Te) phase were because of the inhomogeneously distributed Se and Te, which changes the pinning mechanism from surface pinning in the undoped s le to Δκ pinning in the 5% F-doped one. As a result, the critical current, upper critical field, and thermally activated flux-flow activation energy of FeSe
Publisher: IOP Publishing
Date: 09-2020
Publisher: American Physical Society (APS)
Date: 29-12-2020
Publisher: Elsevier BV
Date: 05-2022
Publisher: American Chemical Society (ACS)
Date: 27-08-2019
Publisher: American Physical Society (APS)
Date: 26-03-2015
Publisher: American Physical Society (APS)
Date: 14-09-2020
Publisher: Springer Science and Business Media LLC
Date: 08-04-2017
Publisher: Springer Science and Business Media LLC
Date: 12-11-2019
DOI: 10.1038/S41535-019-0195-7
Abstract: As personal electronic devices increasingly rely on cloud computing for energy-intensive calculations, the power consumption associated with the information revolution is rapidly becoming an important environmental issue. Several approaches have been proposed to construct electronic devices with low-energy consumption. Among these, the low-dissipation surface states of topological insulators (TIs) are widely employed. To develop TI-based devices, a key factor is the maximum temperature at which the Dirac surface states dominate the transport behavior. Here, we employ Shubnikov-de Haas oscillations (SdH) as a means to study the surface state survival temperature in a high-quality vanadium doped Bi 1.08 Sn 0.02 Sb 0.9 Te 2 S single crystal system. The temperature and angle dependence of the SdH show that: (1) crystals with different vanadium (V) doping levels are insulating in the 3–300 K region (2) the SdH oscillations show two-dimensional behavior, indicating that the oscillations arise from the pure surface states and (3) at 50 K, the V 0.04 single crystals (V x :Bi 1.08- x Sn 0.02 Sb 0.9 Te 2 S, where x = 0.04) still show clear sign of SdH oscillations, which demonstrate that the surface dominant transport behavior can survive above 50 K. The robust surface states in our V doped single crystal systems provide an ideal platform to study the Dirac fermions and their interaction with other materials above 50 K.
Publisher: Springer Science and Business Media LLC
Date: 23-11-2020
DOI: 10.1038/S41377-020-00429-X
Abstract: Magnetic resonances not only play crucial roles in artificial magnetic materials but also offer a promising way for light control and interaction with matter. Recently, magnetic resonance effects have attracted special attention in plasmonic systems for overcoming magnetic response saturation at high frequencies and realizing high-performance optical functionalities. As novel states of matter, topological insulators (TIs) present topologically protected conducting surfaces and insulating bulks in a broad optical range, providing new building blocks for plasmonics. However, until now, high-frequency (e.g. visible range) magnetic resonances and related applications have not been demonstrated in TI systems. Herein, we report for the first time, to our knowledge, a kind of visible range magnetic plasmon resonances (MPRs) in TI structures composed of nanofabricated Sb 2 Te 3 nanogrooves. The experimental results show that the MPR response can be tailored by adjusting the nanogroove height, width, and pitch, which agrees well with the simulations and theoretical calculations. Moreover, we innovatively integrated monolayer MoS 2 onto a TI nanostructure and observed strongly reinforced light–MoS 2 interactions induced by a significant MPR-induced electric field enhancement, remarkable compared with TI-based electric plasmon resonances (EPRs). The MoS 2 photoluminescence can be flexibly tuned by controlling the incident light polarization. These results enrich TI optical physics and applications in highly efficient optical functionalities as well as artificial magnetic materials at high frequencies.
Publisher: American Physical Society (APS)
Date: 19-03-2020
Publisher: Wiley
Date: 23-05-2019
Publisher: AIP Publishing
Date: 16-04-2018
DOI: 10.1063/1.5021637
Abstract: Topological semimetals represent one of the most interesting classes of materials that continue to attract worldwide interest. Here, we report magnetotransport properties of MPn2-type (M = Nb, Ta Pn = P, As, Sb) NbSb2 single-crystal semimetals with a centrosymmetric C12/m1 space group, paramagnetic ground state, and non-saturation parabolic-like magnetoresistance. The NbSb2 crystals show metallic conductivity down to 2 K and undergo a metal-to-insulator-like transition under a magnetic field B (B ≥ 4 T) and exhibit a resistivity plateau in the low-temperature region (T ≤ 10 K), where the value of resistivity strongly depends on the magnitude and direction of the magnetic field. Upon sweeping the magnetic field from 0 to 14.5 T in the transverse configuration at T = 1.5 K, the NbSb2 crystal shows a large positive magnetoresistance (4.2 × 103% at B = 14.5 T) with Shubnikov–de Haas (SdH) oscillation. Hall measurements reveal that both the carrier compensation between electrons and holes and the high mobility and large mean free path of carriers contribute to the large magnetoresistance. Fast Fourier transform analyses of angle-resolved SdH oscillation indicate that the Fermi surface of the NbSb2 crystal is quasi-two-dimensional with three-dimensional components. These findings, together with the theoretically calculated electronic band structure obtained within the framework of density functional theory, suggest that NbSb2 is a good candidate compensated semimetal for further theoretical and experimental investigation of this family of materials.
Publisher: Springer Science and Business Media LLC
Date: 23-11-2022
Publisher: American Physical Society (APS)
Date: 13-03-2023
Publisher: American Physical Society (APS)
Date: 28-10-2022
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 10-2023
Publisher: American Chemical Society (ACS)
Date: 13-05-2019
Publisher: Springer Science and Business Media LLC
Date: 27-03-2023
DOI: 10.1038/S41467-023-37102-X
Abstract: The conducting boundary states of topological insulators appear at an interface where the characteristic invariant ℤ 2 switches from 1 to 0. These states offer prospects for quantum electronics however, a method is needed to spatially-control ℤ 2 to pattern conducting channels. It is shown that modifying Sb 2 Te 3 single-crystal surfaces with an ion beam switches the topological insulator into an amorphous state exhibiting negligible bulk and surface conductivity. This is attributed to a transition from ℤ 2 = 1 → ℤ 2 = 0 at a threshold disorder strength. This observation is supported by density functional theory and model Hamiltonian calculations. Here we show that this ion-beam treatment allows for inverse lithography to pattern arrays of topological surfaces, edges and corners which are the building blocks of topological electronics.
Publisher: American Physical Society (APS)
Date: 23-04-2019
Publisher: American Physical Society (APS)
Date: 15-10-2021
Publisher: Elsevier BV
Date: 2021
Publisher: Springer Science and Business Media LLC
Date: 19-10-2018
DOI: 10.1038/S41535-018-0125-0
Abstract: Reversible and nonvolatile electric-field control of the physical properties of topological insulators is essential for fundamental research and development of practical electronic devices. Here, we report the integration of topological insulator films with ferroelectric Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMN-PT) single crystals in the form of ferroelectric field-effect devices that allow us to tune the electronic properties of topological insulator films in a reversible and nonvolatile manner. Specifically, gating of Cr-doped Bi 2 Se 3 films with the PMN-PT layer is shown to provide a means to reversibly tune and modulate the carrier density and carrier type, as well as its other properties, such as the conductance, magnetoconductance, Fermi level, phase coherence length, and screening factor of electron–electron interaction by polarization switching at room temperature. These findings provide a simple and direct approach for probing the quantum transport properties of topological insulator films through ferroelectric gating by using PMN-PT. The combination of topological insulators with both ferroelectrically and piezoelectrically active PMN-PT thus offers a promising step toward exploring topological insulator/ferroelectric(piezoelectric) hybrid devices that could utilize not only the ferroelectric field-effect of topological insulator/PMN-PT structures but also the unique properties of respective materials.
Publisher: AIP Publishing
Date: 18-07-2023
DOI: 10.1063/5.0157590
Abstract: Two-dimensional electron gas is precisely confined at the interface of insulating oxide thin films and substrates, e.g., LaAlO3/SrTiO3(STO) and, thus, shows 2D electronic transport features. Here, we report a high mobility electron state at the interface of a Cr2O3 film and a STO substrate, which is realized by depositing a Cr film onto a STO (111) substrate in high vacuum (1 × 10−10 mbar) using molecular beam epitaxy. At a substrate temperature of 700 °C, the deposited Cr films capture oxygen atoms from STO substrates, resulting in the formation of an insulating Cr2O3 layer and an oxygen-deficient STO layer. Due to the presence of high mobility electrons [1.5 × 104 cm2V−1 s−1 at 1.8 K] at the Cr2O3/STO interface, both out-of-plane and in-plane Shubnikov–de Haas oscillations are observed at low temperatures (& K), which suggests that the highly conducting electron gas has extended into the STO bulk along the thickness direction with a certain depth to allow electrons to complete the cyclotron motion.
Publisher: IOP Publishing
Date: 12-12-2017
Publisher: Elsevier BV
Date: 08-2019
Publisher: IOP Publishing
Date: 03-10-2023
Publisher: Elsevier BV
Date: 06-2017
Publisher: American Physical Society (APS)
Date: 15-03-2019
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3CP03480A
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0NR01949F
Abstract: Polycrystalline SnSe s le with graphene embedded in realized the enhancement of phonon scattering and achieved ultralow thermal conductivity.
Publisher: IOP Publishing
Date: 24-10-2023
Publisher: AIP Publishing
Date: 11-02-2016
DOI: 10.1063/1.4941105
Abstract: The magnetocaloric effect (MCE) is an intrinsic property of magnetic materials that enable magnetic refrigeration devices without using the traditional vapour-compression. Temperature sensitive and anisotropic magnetic solids might give rise to a large rotating MCE for building compact and efficient magnetic cooling systems by simply rotating the s le. Here, we report an unprecedented maximal refrigeration capacity of 497.36 J/kg (at 70 kOe) in perovskite TbFeO3 single crystal, resulting from its giant anisotropic magnetic entropy change along a axis. Our paper reveals that interaction between Fe-3d and Tb-4f electrons drives extremely interesting spin reorientation transition, which is highly sensitive to magnetic field and temperature. These findings highlight potential applications of an emerging material for high efficient low temperature magnetic refrigeration, which is compact and quiet, and does not use ozone-depleting coolant gases.
Publisher: American Physical Society (APS)
Date: 10-05-2022
Publisher: Elsevier BV
Date: 07-2016
Publisher: AIP Publishing
Date: 11-05-2020
DOI: 10.1063/5.0006447
Abstract: The surfaces of Sb2Te3 topological insulator crystals were implanted using a 40 keV chromium ion beam. To facilitate uniform doping, the Sb2Te3 was passivated with a thin TiO2 film before the implantation step. The resulting chemical structure was studied using atomic-resolution transmission electron microscopy. A fluence of 7 × 1015 ions/cm2 at 40 keV lead to amorphization of the Sb2Te3 surface, with chromium predominantly incorporated in the amorphous layer. Heating to 200 °C caused the amorphous region to recrystallize and led to the formation of a thin chromium-rich interfacial layer. Near-edge x-ray absorption spectroscopy indicates a uniform valence state of Cr3+ throughout, with no evidence of metallic clustering. High-temperature superparamagnetic behavior was detected up to 300 K, with an increased magnetic moment below 50 K.
Publisher: Springer Science and Business Media LLC
Date: 25-11-2016
DOI: 10.1038/SREP37529
Abstract: RFeO 3 orthoferrites, where R is a rare-earth ion of the lanthanide series, are attracting attention mostly because of their promising fast spin dynamics. The magnetic properties of these materials seem to crucially depend on whether the magnetizations of the R and Fe ions’ weak ferromagnetic (WFM) components are parallel or antiparallel to each other. Here, we report an extensive investigation of a high-quality DyFeO 3 single crystal in which the induced Dy 3+ magnetization (F Dy ) has a natural tendency to be antiparallel to Fe 3+ sublattice magnetization (F Fe ) within a large temperature window. Moreover, we find that specific variations of temperature and applied magnetic fields allow us to make F Dy parallel to F Fe , or force a spin-flip transition in F Fe , among other effects. We found three different magnetic states that respond to temperature and magnetic fields, i.e. linear versus constant or, alternatively, presenting either behavior depending on the history of the s le. An original magnetic field-versus-temperature phase diagram is constructed to indicate the region of stability of the different magnetic phases, and to reveal the precise conditions yielding sudden spin switching and reversals. Knowledge of such a phase diagram is of potential importance to applications in spintronics and magnetic devices.
Publisher: Elsevier BV
Date: 10-2022
Publisher: Elsevier BV
Date: 03-2020
Publisher: American Chemical Society (ACS)
Date: 22-12-2020
Publisher: IOP Publishing
Date: 30-07-2020
Publisher: American Physical Society (APS)
Date: 24-05-2018
Publisher: American Chemical Society (ACS)
Date: 27-09-2016
Abstract: We report the epitaxial growth of oxygen deficient titanium dioxide thin films on 0.7Pb(Mg
No related grants have been discovered for Weiyao Zhao.