Article
Physics, Condensed Matter
Y. H. Zan, S. L. Ban
Summary: In symmetric MgxZn1-xO/ZnO quantum wells, the electron states and optical phonon modes are clarified using the dielectric continuum model, uniaxial model, and force balance equation. The electronic mobility affected by optical phonons is obtained through a weight model considering mixed phases in MgxZn1-xO. Results show fluctuations in QW's barriers in mixed phases region and different influences of WZ and RS phases on electronic mobility in HEMTs design.
SUPERLATTICES AND MICROSTRUCTURES
(2021)
Article
Materials Science, Multidisciplinary
S. K. Chetia, P. Rajput, R. S. Ajimsha, R. Singh, A. K. Das, R. Kumar, P. S. Padhi, A. K. Sinha, S. N. Jha, T. K. Sharma, P. Misra
Summary: MgxZn1-xO thin films with wide range bandgap tunability from approximately 3.28 to 6.7 eV were grown on (0001) Sapphire substrates using RF magnetron co-sputtering method. The bandgap of MgxZn1-xO increased gradually from around 3.28 to 4.45 eV with Mg content 0 <= x <= 0.51 and from around 5.55 to 6.7 eV for Mg content 0.55 <= x <= 1, with a sudden jump of about 1.1 eV at x > 0.51. The structure of the MgxZn1-xO films exhibited hexagonal wurtzite phase for Mg content x <= 0.51 and cubic rock salt phase for Mg content >= 0.55, without any mixed phase. X-ray absorption near edge structure (XANES) measurements showed distinct changes in the spectra for wurtzite phase with Mg content x = 0.09, indicating a phase transformation, while no significant change was observed for the cubic phase with Mg content x = 0.73. EXAFS measurements revealed the presence of sixfold Zn coordination in the wurtzite phase of high Mg content MgxZn1-xO films, along with distortion in the bond lengths of Zn-O and Zn-Zn/Mg pairs.
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
(2022)
Article
Materials Science, Multidisciplinary
Qiuliang Zhong, Cheng Wu, Xiaoming Yu, Xuan Yu, Zhenhua Li, Qian Qiao, Yingtang Zhou, Yu Cao
Summary: In recent years, self-powered Schottky ultraviolet photodetectors have gained attention due to their low cost and zero-bias response. However, weak light response has limited the development of high-performance self-powered Schottky devices. In this study, the introduction of a MgxZn1-xO capping layer improved the device performance, resulting in increased photocurrent, responsivity, and linear dynamic range.
Article
Physics, Multidisciplinary
Yuan Liu, Zhongran Liu, Meng Zhang, Yanqiu Sun, He Tian, Yanwu Xie
Summary: A crystalline-orientation-dependent two-dimensional superconductivity was found at interfaces between KTaO3 single-crystal substrates and films of other oxides. Epitaxially grown LaVO3/KTaO3(111) heterostructures exhibit superconductivity with a transition temperature of around 0.5 K, while no superconductivity was observed in the (001)- and (110)-orientated heterostructures. To enable conductivity in LaVO3/KTaO3(111) interfaces, an oxygen-deficient growth environment and a minimum LaVO3 thickness of about 0.8 nm (around 2 unit cells) are required.
Article
Chemistry, Multidisciplinary
Anil Kumar Rajapitamahuni, Anusha Kamath Manjeshwar, Avinash Kumar, Animesh Datta, Praneeth Ranga, Laxman Raju Thoutam, Sriram Krishnamoorthy, Uttam Singisetti, Bharat Jalan
Summary: In this study, the highly reversible, electrostatic doping of beta-Ga2O3 films with tunable carrier densities using ion-gel-gated electric double-layer transistor configuration was reported. The plasmon-phonon coupling that dictates electron transport properties was investigated, and it was found that the room-temperature mobility initially increased and then decreased with increasing carrier density due to the plasmon-phonon coupling. The study also revealed the important antiscreening effect arising from dynamic screening of the electron-phonon interactions from the hybrid plasmon-phonon modes. Higher room-temperature mobility can be achieved by harnessing the dynamic screening of the electron-phonon interactions.
Article
Engineering, Electrical & Electronic
DongFeng Liu
Summary: Electron transport in MgxZn1-xO/ZnO heterostructures at room temperature is simulated using the ensemble Monte Carlo method. Various electron scattering mechanisms are considered, and it is found that electron escape scattering is a main limiting factor for drift velocity, while the competition between interface roughness and intersubband polar optical phonon scattering plays an important role in electron drift velocity change with increasing Mg mole fractions.
JOURNAL OF COMPUTATIONAL ELECTRONICS
(2023)
Article
Physics, Applied
Ping Wang, Ding Wang, Shubham Mondal, Zetian Mi
Summary: In this study, robust ferroelectricity was demonstrated in single-crystalline thin films. The crystallographic alignment was confirmed using x-ray diffraction measurements. The highly uniform coercive field and remnant polarization were observed in the nearly lattice-matched heterostructure. The reliability of the ferroelectricity was systematically characterized and showed negligible degradation after a large number of switching cycles. This research provides a feasible pathway for fully epitaxial integration of ferroelectricity into nitride heterostructures, with important applications in various fields.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Mingqun Yang, Tian Du, Xuxia Zhao, Xuelong Huang, Langheng Pan, Shuting Pang, Haoran Tang, Zhongxiang Peng, Long Ye, Yunfeng Deng, Mingliang Sun, Chunhui Duan, Fei Huang, Yong Cao
Summary: The study reports the successful use of intrinsic quinoidal building block, BDP, in constructing conjugated polymers with high electron mobility and unipolar transport characteristics in modified organic field-effect transistors. By incorporating PEIE as the interlayer, reliable electron mobility was achieved in the devices, marking a significant step in exploring intrinsic quinoidal CPs for potential applications in n channel OFETs and logic complementary circuits.
SCIENCE CHINA-CHEMISTRY
(2021)
Article
Chemistry, Multidisciplinary
Zeng Wu, Wentao Liu, Xin Yang, Wenhao Li, Lingli Zhao, Kai Chi, Xuetao Xiao, Yongkun Yan, Weixuan Zeng, Yunqi Liu, Huajie Chen, Yan Zhao
Summary: A series of novel highly π-extended tetracyano-substituted acene diimides (TCDADIs) were synthesized using a simple four-fold Knoevenagel condensation strategy. These compounds have a large π-conjugated backbone and in-situ formation of four cyano substituents, avoiding extra cyano-functionalization reactions. TCDADIs with different N-alkyl substituents exhibit good solubility, near-coplanar backbones, good crystallinity, and low-lying lowest unoccupied molecular orbital energies, leading to desirable electron-transport performance in organic field-effect transistors (OFETs). The highest electron mobility of an OFET based on a 2-hexyldecyl-substituted TCDADI single crystal reaches 12.6 cm(2) V-1 s(-1), which is among the highest values for reported n-type organic semiconductor materials (OSMs).
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Physics, Applied
Simran Arora, Subhabrata Dhar
Summary: The electroluminescence properties of n(+)-ZnO/p-GaN pn(+)-heterojunctions grown epitaxially have been investigated as a function of applied bias and temperature. The study reveals the presence of indirect interfacial excitons at lower temperatures. The electroluminescence feature associated with these excitons is redshifted with increasing forward bias. The formation of these excitons becomes unsustainable when the applied bias or temperature exceeds a threshold due to leakage and thermal escape of charges.
APPLIED PHYSICS LETTERS
(2023)
Article
Crystallography
A. Benali, P. Rajak, R. Ciancio, J. R. Plaisier, S. Heun, G. Biasiol
Summary: This study investigates the influence of strain-relieving InAlAs buffer layers on metamorphic InAs/InGaAs quantum wells grown on GaAs by molecular beam epitaxy. By carefully choosing the composition profile and thicknesses of the buffer layer, virtually unstrained InGaAs barriers can embed InAs quantum wells with high thickness. This technique allows for higher low-temperature electron mobilities than previously reported for metamorphic growth on GaAs, comparable to those achieved for samples grown on InP substrates.
JOURNAL OF CRYSTAL GROWTH
(2022)
Article
Chemistry, Multidisciplinary
Isabel Streicher, Stefano Leone, Christian Manz, Lutz Kirste, Mario Prescher, Patrick Waltereit, Michael Mikulla, Rudiger Quay, Oliver Ambacher
Summary: In this study, AlScN/GaN heterostructures were grown and characterized to investigate the effect of diffusion of AlGaN on 2DEG confinement. The presence of interlayers and the growth temperature were found to significantly affect the sheet carrier density and electron mobility.
CRYSTAL GROWTH & DESIGN
(2023)
Article
Chemistry, Multidisciplinary
Weifeng Zhang, Keli Shi, Jing Lai, Yankai Zhou, Xuyang Wei, Qian Che, Jinbei Wei, Liping Wang, Gui Yu
Summary: Two novel donor-acceptor copolymers, PNFFN-DTE and PNFFN-FDTE, are designed and synthesized for fabricating polymer field-effect transistors (PFETs). The PNFFN-FDTE-based PFETs processed with a bicomponent solvent exhibit the highest electron mobility reported so far, which is attributed to the fully locked conjugated backbone and dense molecular packing of PNFFN-FDTE.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Yang Lu, Jun Chen, Matthew J. Coupin, Sapna Sinha, Jamie H. Warner
Summary: It is demonstrated in this study that vertical layered heterostructures (VLHs) exhibit small twist angles controlled by low energy and local atomic relaxation, contrary to the commonly believed 0 degrees-orientation in van der Waals (vdWs) epitaxy. Moreover, high-mismatch VLHs show discrete and sometimes non-zero twist angles dependent on their natural mismatch value.
ADVANCED MATERIALS
(2022)
Article
Nanoscience & Nanotechnology
Mehdi Akbari-Saatlu, Marcin Procek, Claes Mattsson, Goran Thungstrom, Tobias Torndahl, Ben Li, Jiale Su, Wenjuan Xiong, Henry H. Radamson
Summary: Designing heterostructure materials at the nanoscale is a well-known method to enhance gas sensing performance. In this study, ZnO/SnO2 heterostructures were grown on alumina substrates using the ultrasonic spray pyrolysis method. The results showed that the sensitivity of the sensor to H2S gas can be altered by changing the zinc chloride content in the precursor, and the heterostructures with a 5:1 ratio of ZnCl2 to SnCl2·2H(2)O exhibited the highest response. The gas sensing mechanism of the ZnO/SnO2 heterostructures was analyzed and attributed to the formation of the heterostructure between ZnO and SnO2.
ACS APPLIED NANO MATERIALS
(2022)
Article
Physics, Applied
Suguri Uchida, Takuto Soma, Miho Kitamura, Hiroshi Kumigashira, Akira Ohtomo
Summary: This study reports the growth of SnO films on specific substrates and demonstrates the significant impact of surface treatment on optical transparency, resulting in enhanced visible transmittance of the films. This enhancement is attributed to the suppression of midgap states near the film surface.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Junichi Shiogai, Zhenhu Jin, Yosuke Satake, Kohei Fujiwara, Atsushi Tsukazaki
Summary: A ferromagnetic nanocrystalline Fe-Sn is a suitable platform for magnetic-field sensor based on anomalous Hall effect (AHE) due to its simple fabrication and superior thermal stability. Doping impurity and increasing injection current are effective approaches for enhancing the magnetic-field sensitivity. However, large current may result in increased voltage noise, affecting the magnetic-field detectivity. In this study, a maximum allowable current was improved by using an overlayer electrode configuration on a Ta-doped Fe-Sn AHE sensor. The detectivity was significantly improved at high frequency, showing ten times improvement compared to the non-doped Fe-Sn AHE sensor.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
J. Falson, I. Sodemann, B. Skinner, D. Tabrea, Y. Kozuka, A. Tsukazaki, M. Kawasaki, K. von Klitzing, J. H. Smet
Summary: The study investigates low-temperature phases of strongly interacting electrons using zinc oxide-based two-dimensional electron systems, revealing correlated metallic and insulating states, non-monotonic spin polarizability, and a significant positive magnetoresistance. These findings establish zinc oxide as a platform for studying strongly correlated electrons in two dimensions.
Article
Physics, Multidisciplinary
M. Mogi, Y. Okamura, M. Kawamura, R. Yoshimi, K. Yasuda, A. Tsukazaki, K. S. Takahashi, T. Morimoto, N. Nagaosa, M. Kawasaki, Y. Takahashi, Y. Tokura
Summary: In this study, the half-integer quantization of Hall conductance was observed in a synthetic heterostructure called a semi-magnetic topological insulator. The results provide evidence of the condensed matter realization of the parity anomaly and offer a new way to study the physics enabled by a single Dirac fermion.
Article
Physics, Multidisciplinary
Yuma Okazaki, Takehiko Oe, Minoru Kawamura, Ryutaro Yoshimi, Shuji Nakamura, Shintaro Takada, Masataka Mogi, Kei S. Takahashi, Atsushi Tsukazaki, Masashi Kawasaki, Yoshinori Tokura, Nobu-Hisa Kaneko
Summary: The quantum anomalous Hall effect (QAHE) is a transport phenomenon where the Hall resistance is quantized to the von Klitzing constant, with a precision of 10 parts per billion demonstrated in this study. By directly comparing QAHE with the quantum Hall effect (QHE), it has been confirmed that QAHE meets the required level of quantization accuracy as a primary standard of electric resistance. This high accuracy of quantization is achieved by using a weak magnetic field supplied by a permanent disc magnet to align the magnetization domains, paving the way for developing a quantum resistance standard without strong magnetic fields.
Article
Physics, Applied
Shuxin Zhang, Tatsuya Yajima, Takuto Soma, Akira Ohtomo
Summary: In this study, two polymorphs of MoO3 were epitaxially grown on the (100) plane of cubic perovskites using pulsed-laser deposition. The impacts of Li-ion intercalation on each phase were investigated through electrochemical testing. The alpha-MoO3 films transformed to an amorphous phase after a single electrochemical cycle, while the beta-MoO3 films showed reversible cyclic voltammogram against repeated electrochemical cycles.
APPLIED PHYSICS EXPRESS
(2022)
Article
Physics, Applied
Junichi Shiogai, Kohei Fujiwara, Tsutomu Nojima, Atsushi Tsukazaki
Summary: This study investigates the structural dependence of UMR in Fe-Sn heterostructure devices, revealing a weak dependence of UMR on interface configuration but an enhancement in UMR amplitude with increasing Fe-Sn layer thickness.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Kohei Fujiwara, Koya Shibata, Shunsuke Nishimura, Junichi Shiogai, Atsushi Tsukazaki
Summary: The effect of annealing on the crystalline ordering and physical properties in thin films of Co2FeSn is reported. The annealing process induced structural changes and significantly influenced the electrical and thermoelectric transport properties. These findings highlight the importance of annealing in studying the topological band features in Co2FeSn thin films.
Article
Materials Science, Multidisciplinary
Yoshihiro D. Kato, Yoshihiro Okamura, Susumu Minami, Reika Fujimura, Masataka Mogi, Ryutaro Yoshimi, Atsushi Tsukazaki, Kei S. Takahashi, Masashi Kawasaki, Ryotaro Arita, Yoshinori Tokura, Youtarou Takahashi
Summary: This research reveals that the large intrinsic anomalous Hall effect in the ferromagnetic nodal line semimetal Fe3GeTe2 is generated by the cooperation of flat bands and band crossings near the Fermi level. The study finds that two resonance structures in the terahertz and infrared magneto-optical spectroscopy are closely related to the anomalous Hall effect.
NPJ QUANTUM MATERIALS
(2022)
Article
Physics, Applied
Junichi Shiogai, Atsushi Tsukazaki
Summary: In this study, a freestanding single-crystalline FeSe membrane was prepared using a water-soluble Sr3Al2O6 sacrificial layer as a growth template. The FeSe membrane was fully relaxed with minimal degradation of its structural properties during the lift-off process. The freestanding FeSe membrane exhibited superconductivity below 4.2 K, while it was not observed in a compressed thin-film form.
APPLIED PHYSICS LETTERS
(2023)
Letter
Physics, Multidisciplinary
Minoru Kawamura, Masataka Mogi, Ryutaro Yoshimi, Takahiro Morimoto, Kei S. Takahashi, Atsushi Tsukazaki, Naoto Nagaosa, Masashi Kawasaki, Yoshinori Tokura
Summary: Adiabatic charge pumping is observed in a thin-film magnetic heterostructure of topological insulators, confirming the theoretical prediction of topological magnetoelectric effect. The pumped charge is proportional to the surface Hall conductivity, providing clues for its direct observation.
Article
Physics, Applied
Kohei Fujiwara, Junya Ikeda, Shun Ito, Atsushi Tsukazaki
Summary: Solid-liquid interfaces composed of functional inorganic materials and liquid electrolytes exhibit interesting responses when an electric bias is applied. By using an electric-double-layer device on a thin-film channel of magnetic Weyl semimetal Co3Sn2S2 with an ionic liquid gate electrolyte, it is shown that the thickness of the conducting channel can be effectively reduced with a negative gate voltage. This finding allows for the examination of the thickness dependence of the anomalous transport properties of Co3Sn2S2 in a single sample.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Masamichi Negishi, Kohei Fujiwara, Atsushi Tsukazaki
Summary: Pulsed-laser deposition is a widely used method to fabricate complex oxide thin films, and film composition is regulated by various conditions. This study reports an experimental scheme to tune the composition ratio in Mg-Ir-O films fabricated by pulsed-laser deposition. By examining different parameters, a wide range of composition ratio was regulated in the films, and a spinel-related crystalline phase was discovered in the Mg-rich compositions.
Article
Multidisciplinary Sciences
Kohei Fujiwara, Yasuyuki Kato, Hitoshi Abe, Shun Noguchi, Junichi Shiogai, Yasuhiro Niwa, Hiroshi Kumigashira, Yukitoshi Motome, Atsushi Tsukazaki
Summary: Amorphous semiconductors are widely used in electronic and energy-conversion devices. This study reveals that the short-range crystalline order in amorphous Fe-Sn films contributes to anomalous electrical and magneto-thermoelectric properties. This finding sheds light on the topology of amorphous materials and may enable the realization of functional topological amorphous electronic devices.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Motoki Osada, Kohei Fujiwara, Tsutomu Nojima, Atsushi Tsukazaki
Summary: The nickelate superconductor with infinite NiO2 layer was synthesized by reducing the perovskite precursor phase through topochemical reduction. By increasing the reduction temperature, La1-xSrxNiO2 films transformed from the insulating state to the superconducting state, with a maximum onset superconducting transition temperature T onset c of about 14K at x = 0.20. The electrical conduction in NiO2 planes is found to be a sensitive parameter for optimizing the reduction state. The systematic optimization of reduction temperature resulted in an expanded superconducting dome in the phase diagram with higher T onset c and wider x range (0.12 x 0.28) compared to previous reports.
PHYSICAL REVIEW MATERIALS
(2023)
