Article
Physics, Applied
J. X. Wang, Y. Qu, S. L. Ban
Summary: This study investigates the effects of asymmetric MgZnO barriers on electron mobility and reveals the contributions of four asymmetric quantum wells to electron mobility and the asymmetry caused by the built-in electric field. The results show that wurtzite barriers are more favorable for achieving stable high mobility.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Multidisciplinary
Qing-Fen Jiang, Jie Lian, Min-Ju Ying, Ming-Yang Wei, Chen-Lin Wang, Yu Zhang
Summary: The structures, morphologies, and optical properties of Zn-polar ZnO films modified by ion implantation with different concentrations of krypton ions were investigated. The absorption spectrum, photoluminescence, and spectroscopic ellipsometry results showed that krypton ion implantation led to increased absorption, reduced bandgap, and decreased refractive index in the films. This study contributes to the design and optimization of krypton ion-implanted polar ZnO films for optoelectronic applications.
Article
Physics, Multidisciplinary
Xin Liang, Hua Zhou, Hui-Qiong Wang, Lihua Zhang, Kim Kisslinger, Junyong Kang
Summary: Zn1-xMgxO alloy films, important for deep ultraviolet photoelectric applications, were successfully prepared with varying magnesium contents using plasma-assisted molecular beam epitaxy on both polar and nonpolar substrates in this work.
Article
Chemistry, Physical
Ning Wang, Peng Wang, Fengzhi Wang, Haiping He, Jinyun Huang, Xinhua Pan, Guangming Zhu, Jiangbo Wang, Zhizhen Ye
Summary: This study investigates the growth of ZnO film on a graphene-buffered sapphire substrate using plasma-assisted molecular beam epitaxy (PAMBE). The results show that the crystal quality of ZnO film can be improved by buffering it with double-layer graphene (DLG), leading to the formation of symmetric pits on the film surface. The findings have implications for the development of simplified growth technology for ZnO-based films and devices.
APPLIED SURFACE SCIENCE
(2022)
Article
Physics, Multidisciplinary
Xiang-Peng Zhou, Hai-Bing Qiu, Wen-Xian Yang, Shu-Long Lu, Xue Zhang, Shan Jin, Xue-Fei Li, Li-Feng Bian, Hua Qin
Summary: AlN/GaN resonant tunneling diodes (RTDs) grown on freestanding GaN substrates exhibit room temperature negative differential resistance (NDR) and two resonance peaks, with lower dislocation densities, flatter surface morphology, and steeper heterogeneous interfaces being key factors for achieving NDR.
Article
Chemistry, Physical
Aleksey Nikolaevich Klochkov, Aleksander Nikolaevich Vinichenko, Artyom Alekseevich Samolyga, Sergey Mihailovich Ryndya, Maksim Viktorovich Poliakov, Nikolay Ivanovich Kargin, Ivan Sergeevich Vasil'evskii
Summary: This study explores silicon doped indium arsenide polycrystalline thin films grown on c-oriented alpha-sapphire substrates by molecular beam epitaxy. The structural and transport properties of the films are investigated, showing electron mobility of about 600 cm(2)/V·s at room temperature and excellent temperature stability of electrophysical properties in the range of 80-320 K. The use of an InAlAs seed layer during the initial growth stage is found to reduce the roughness and width of the n-InAs films, indicating the potential for temperature stable Hall effect magnetic field sensors based on InAs.
APPLIED SURFACE SCIENCE
(2023)
Article
Physics, Applied
D. N. Lobanov, K. E. Kudryavtsev, M. Kalinnikov, L. Krasilnikova, P. A. Yunin, E. Skorokhodov, M. Shaleev, A. Novikov, B. A. Andreev, Z. F. Krasilnik
Summary: This study reports on stimulated emission (SE) in the near-infrared range from planar InGaN epitaxial layers grown on sapphire substrates. The research found that at temperatures around 190-210K, nonradiative recombination processes dominate the temperature quenching of stimulated emission. Different defect centers play a role in providing free electrons for both InN and InGaN layers, affecting the Shockley-Read-Hall (SRH) recombination rate at high temperatures.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
I. Ahmed, S. De Gendt, C. Merckling
Summary: The BaBiO3 perovskite oxide is an interesting material system that exhibits superconductivity when p-doped and predicted topological insulation when n-doped. High-quality single crystalline BaBiO3 films are grown on Si(001) substrates using molecular beam epitaxy, with the growth window established by systematically varying growth parameters.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Stanislav Tiagulskyi, Roman Yatskiv, Hana Faitova, Ondrej Cernohorsky, Jan Vanis, Jan Grym
Summary: The experimental approach demonstrated in this study prototypes heterojunctions between graphene and bulk semiconductor substrates using focused ion beam milling and in-situ electrical measurements. The aim is to limit the impact of defects in graphene on the electrical characteristics of the junctions. The approach is successfully applied to graphene/ZnO structures and experimentally validates theoretical predictions of differences in charge transport.
PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES
(2022)
Article
Physics, Condensed Matter
Mario Littmann, Dirk Reuter, Donat Josef As
Summary: Remote epitaxy, a new area of research, has the potential to reduce lattice mismatch and simplify film exfoliation. This study focuses on applying this growth method to cubic gallium nitride (c-GaN), a metastable phase. However, nucleating the metastable cubic phase is challenging due to weaker interactions between the substrate and the epitaxial layer. Initially, only polycrystalline wurtzite gallium nitride could be grown, but by optimizing conditions and adding a cubic aluminum nitride buffer layer, predominantly cubic gallium nitride layers can be grown. High-resolution X-ray diffraction measurements confirm a reduction in hexagonal inclusions from 80% to 23%.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2023)
Article
Physics, Applied
Yingfeng He, Yimeng Song, Huiyun Wei, Peng Qiu, Heng Liu, Xiaoli Zhu, Feng Tian, Mingzeng Peng, Xinhe Zheng
Summary: In this study, GaN thin films were grown on a sapphire substrate with a graphene interlayer using plasma-enhanced atomic layer deposition (PEALD). The results from X-ray diffraction and transmission electron microscopy confirmed the nearly single-crystalline nature of the GaN thin films. Additionally, the interfacial properties and nucleation behaviors of GaN thin films deposited on graphene were investigated in detail. Therefore, this study offers a new perspective on PEALD growth of high-quality nanoscale GaN epilayers and expands the options for low-temperature fabrication of GaN-based devices.
APPLIED PHYSICS LETTERS
(2023)
Article
Crystallography
Amalia Fernando-Saavedra, Steven Albert, Ana Bengoechea-Encabo, Achim Trampert, Mengyao Xie, Miguel A. Sanchez-Garcia, Enrique Calleja
Summary: Non-polar m-plane GaN films were grown on & gamma;-LiAlO2 (100) substrates using a two-step process that involved coalescence of GaN nanocolumns obtained from a GaN buffer. Transmission electron microscopy data showed a significant reduction in extended defects density in the coalesced film compared to the initial GaN buffer, likely due to a filter effect during the regrowth process. Low temperature photoluminescence spectra confirmed this reduction in defects, with a decrease in stacking faults emission peaks and a dominant donor-bound excitonic emission at 3.472 eV.
JOURNAL OF CRYSTAL GROWTH
(2023)
Article
Materials Science, Multidisciplinary
Nutthapong Discharoen, Sakuntam Sanorpim, Noppadon Nuntawong, Visittapong Yordsri, Suphakan Kijamnajsuk, Kentaro Onabe
Summary: Cubic AlN films were successfully grown on MgO substrates using a two-step cubic GaN buffer layer. The two-step buffer layer was found to play a crucial role in the epitaxial growth of c-AlN, resulting in improved crystallinity compared to one-step and nonGaN buffer layers.
Article
Chemistry, Multidisciplinary
Liesbeth Mulder, Daan H. Wielens, Yorick A. Birkholzer, Alexander Brinkman, Omar Concepcion
Summary: In this study, ultrathin films of the ternary topological insulator (Bi0.4Sb0.6)(2)Te-3 were fabricated using molecular beam epitaxy. The influence of the substrate on the formation of defects, mosaicity, and twin domains was found to be significant.
Article
Crystallography
Nurzal Nurzal, Wei-Cyuan Huang, Cheng-Yu Liu, Su-Hua Chen, Ing-Song Yu
Summary: In this study, quantum dots of hexagonal boron nitride (h-BN) were successfully fabricated on the surface of polycrystalline Ni film using plasma-assisted molecular beam epitaxy. The existence of the h-BN quantum dots was confirmed through various characterization techniques, including scanning electron microscopy and atomic force microscopy. The study also investigated the effect of temperature on the growth parameters for the quantum dots.
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
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
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
Chemistry, Physical
Saskia Schimmel, Michael Salamon, Daisuke Tomida, Steffen Neumeier, Tohru Ishiguro, Yoshio Honda, Shigefusa F. Chichibu, Hiroshi Amano
Summary: An in situ monitoring technique for tracking mass transport of the nitride in the ammonothermal method was evaluated using high-energy computed tomography. Suitable transparency in the autoclave volume can be achieved in a lab-scale setup for GaN crystal growth. For ammonoacidic growth, shorter scan durations or lower acceleration voltages are feasible.
Article
Materials Science, Multidisciplinary
Makoto Masuko, Minoru Kawamura, Ryutaro Yoshimi, Motoaki Hirayama, Yuya Ikeda, Ryota Watanabe, James Jun He, Denis Maryenko, Atsushi Tsukazaki, Kei S. Takahashi, Masashi Kawasaki, Naoto Nagaosa, Yoshinori Tokura
Summary: In a hybrid system of topological insulator/superconductor, researchers have discovered topological superconductivity in a Bi2Te3/PdTe2 heterostructure. This heterostructure is characterized by tellurium compounds, epitaxial growth, and a small charge transfer interface.
NPJ QUANTUM MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Y. Okamura, H. Handa, R. Yoshimi, A. Tsukazaki, K. S. Takahashi, M. Kawasaki, Y. Tokura, Y. Takahashi
Summary: This study investigates the lattice and charge dynamics in ferroelectric semiconductor thin films using terahertz time-domain spectroscopy. The results show that there is a temperature anomaly in the resonant frequency of the phonons, indicating a displacive-type ferroelectric transition. The study also reveals an enhancement of ferroelectricity in the films and the ability of low-energy phonons to induce a large dielectric constant even in metallic states.
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
Materials Science, Multidisciplinary
Junichi Shiogai, Junya Ikeda, Kohei Fujiwara, Takeshi Seki, Koki Takanashi, Atsushi Tsukazaki
Summary: By measuring Hall resistance, we found that the Co3Sn2S2 thin films have a large coercivity, which is attributed to the uniform crystallinity within grains and strong domain-wall pinning at grain boundaries. This is important for controlling the nucleation, manipulation, and detection of single domain walls in thin-film devices.
PHYSICAL REVIEW MATERIALS
(2022)
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)
Article
Materials Science, Multidisciplinary
Takuto Soma, Kohei Yoshimatsu, Koji Horiba, Hiroshi Kumigashira, Akira Ohtomo
Summary: The oxide superconductor Li1-xNbO2, with two-dimensional NbO2 layers, exhibits 2D superconductivity and large anisotropy in the upper critical field. The temperature-independent anisotropy suggests single-band superconductivity, which is different from other materials with similar structures. The study also reveals a narrow and correlated single band in the 2D NbO2 layers of Li1-xNbO2, similar to the superconductivity in cuprates.
