Article
Chemistry, Multidisciplinary
Babak Nikoobakht, Aaron C. Johnston-Peck, David Laleyan, Ping Wang, Zetian Mi
Summary: A novel approach was presented for growth of surface-directed spinel ZnGa2O4 and beta-Ga2O3 nanofins coated with a non-polar GaN shell, utilizing a vacancy-assisted mechanism for exchange between Zn and Ga. The predictability over surface registries and tunable porosity of the core/shell fins is anticipated to be significant for various applications.
Article
Chemistry, Multidisciplinary
Yi-Fan Zhao, Ling-Jie Zhou, Fei Wang, Guang Wang, Tiancheng Song, Dmitry Ovchinnikov, Hemian Yi, Ruobing Mei, Ke Wang, Moses H. W. Chan, Chao-Xing Liu, Xiaodong Xu, Cui-Zu Chang
Summary: The study utilized molecular beam epitaxy (MBE) to grow MnBi2Te4 films of various thicknesses and observed a nonsquare hysteresis loop in films with a thickness greater than 2 septuple layers (SL). The hysteresis loop was found to consist of two anomalous Hall (AH) components, one from the dominant MnBi2Te4 phase and the other from the minor Mn-doped Bi2Te3 phase. The AH component extracted from the MnBi2Te4 phase exhibited clear even-odd layer-dependent behavior.
Article
Chemistry, Multidisciplinary
Fei Wang, Yi-Fan Zhao, Zi-Jie Yan, Deyi Zhuo, Hemian Yi, Wei Yuan, Lingjie Zhou, Weiwei Zhao, Moses H. W. Chan, Cui-Zu Chang
Summary: In this study, we synthesized doped Bi2Te3 thin films with controlled doping concentrations using molecular beam epitaxy. By conducting magneto-transport measurements, we observed an unusual ferromagnetic response in both chromium (Cr)- and vanadium (V)-doped films, where the Curie temperature shows a local maximum at a critical doping concentration. We attribute this behavior to the dopant-concentration-induced magnetic exchange interaction, which transforms the ferromagnetism from van Vleck-type in a nontrivial magnetic topological insulator to Ruderman-Kittel-Kasuya-Yosida (RKKY)-type in a trivial diluted magnetic semiconductor. This work provides insights into the ferromagnetic properties of magnetically doped topological insulator thin films and facilitates the exploration of high-temperature quantum anomalous Hall effect.
Article
Chemistry, Multidisciplinary
Isao Ohkubo, Takashi Aizawa, Katsumitsu Nakamura, Takao Mori
Summary: The study found that using thin-film technology can control phase formation, which is advantageous for the preparation of undeveloped materials. To obtain thin films with desired properties, it is necessary to control factors such as crystal orientation, quality, and defect concentration in the thin films. Tuning the competition between thermodynamics and kinetics during vapor-phase thin-film growth is crucial for successfully fabricating high-quality thin films.
FRONTIERS IN CHEMISTRY
(2021)
Article
Materials Science, Multidisciplinary
Tuo Sheng, Xing-Zhao Liu, Ling-Xuan Qian, Bo Xu, Yi-Yu Zhang
Summary: Metal-semiconductor-metal solar-blind ultraviolet photoconductors based on beta-Ga2O3 thin films were fabricated and the effects of annealing on their characteristics and photoconductivity were studied. Higher annealing temperature resulted in lower crystalline quality and device photoresponsivity. The vacuum-annealed sample showed the highest photoresponsivity and the oxygen-annealed sample effectively suppressed persistent photoconductivity.
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
Chemistry, Multidisciplinary
Jonathan R. Chin, Marshall B. Frye, Derrick Shao-Heng Liu, Maria Hilse, Ian C. Graham, Jeffrey Shallenberger, Ke Wang, Roman Engel-Herbert, Mengyi Wang, Yun Kyung Shin, Nadire Nayir, Adri C. T. van Duin, Lauren M. Garten
Summary: Self-limiting stoichiometry promotes the growth of SnSe thin films by maintaining film stoichiometry and controlling crystallographic orientation. Results show that self-limiting stoichiometry can increase the lateral scale of SnSe layers, providing a promising avenue for device fabrication.
Article
Physics, Applied
Minh Anh Phan Nguyen, Jennifer Hite, Michael A. Mastro, Mehran Kianinia, Milos Toth, Igor Aharonovich
Summary: This study investigates the nature of quantum emitters in GaN grown on samples with different growth orientations, revealing consistent formation of quantum emitters in Ga-polar regions. Findings shed light on the origins of these quantum emitters and demonstrate site-selective formation in GaN. Through various tests, the overall defectivity of Ga-polar GaN synthesized using a specific growth procedure is attributed to the formation of quantum emitters.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
A. F. M. Anhar Uddin Bhuiyan, Zixuan Feng, Lingyu Meng, Hongping Zhao
Summary: This tutorial summarizes the recent advances in the epitaxial growth of beta-Ga2O3 thin films using different growth methods, with a particular focus on the growth of Ga2O3 and its alloys by metalorganic chemical vapor deposition (MOCVD). The challenges in the epitaxial development of beta-Ga2O3 are discussed, along with the opportunities for improving device performance based on this emerging ultrawide bandgap semiconductor material system.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
L. Riney, C. Bunker, S. -K. Bac, J. Wang, D. Battaglia, Yun Chang Park, M. Dobrowolska, J. K. Furdyna, X. Liu, B. A. Assaf
Summary: The study reported the synthesis of SrxBi2Se3 thin films and characterized their structural, vibrational, and electrical properties. The results showed that Sr mainly occupies specific sites in Bi2Se3 and undergoes substitution with Bi. Although increasing Sr content leads to increased n-type doping, superconductivity was not observed down to 1.5K.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Tiffany C. Kaspar, Peter Hatton, Kayla H. Yano, Sandra D. Taylor, Steven R. Spurgeon, Blas P. Uberuaga, Daniel K. Schreiber
Summary: Thin film deposition from the vapor phase involves complex adatom adsorption, movement, and incorporation into the growing film. This study provides experimental and simulation evidence for anion intermixing during the deposition process. The research reveals that adatoms on the film surface pull up subsurface oxygen and iron and facilitate their mixing through ring-like rotation mechanisms. These findings contribute to the understanding of thin film deposition and other surface-mediated processes.
Article
Materials Science, Multidisciplinary
Alberto Binetti, Wei-Fan Hsu, Koen Schouteden, Jin Won Seo, Jean-Pierre Locquet, Maria Recaman Payo
Summary: Vanadium sesquioxide (V2O3) is a promising material for new-generation sensors or smart devices due to its strong correlation effects and tunable metal-insulator transitions. The successful growth of epitaxial thin films on silicon substrates has been achieved by adjusting the growth conditions, and extensive characterization has been carried out. Structural analysis reveals the impact of temperature on thin film microstructures, and the lattice mismatch between silicon and V2O3 induces the growth of the corundum PI phase. Additionally, small deviations from stoichiometry significantly affect the resistivity change upon cooling.
RESULTS IN PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Qinghao Meng, Fan Yu, Gan Liu, Junyu Zong, Qichao Tian, Kaili Wang, Xiaodong Qiu, Can Wang, Xiaoxiang Xi, Yi Zhang
Summary: In this article, high-quality beta-In2Se3 thin films were successfully grown on bilayer graphene substrates using molecular beam epitaxy (MBE). The four-monolayer beta-In2Se3 was found to have a (9 x 1) reconstructed superlattice, while the monolayer beta-In2Se3/BLG heterostructure showed a folding Dirac cone due to interfacial interaction and moire superlattice. After potassium doping, the band gap of In2Se3 film decreased and the valence band maximum shifted in momentum. These experimental results provide a new platform for studying 2D ferroelectric heterostructures and devices.
Article
Nanoscience & Nanotechnology
Patrick Vogt, Felix V. E. Hensling, Kathy Azizie, Celesta S. Chang, David Turner, Jisung Park, Jonathan P. McCandless, Hanjong Paik, Brandon J. Bocklund, Georg Hoffman, Oliver Bierwagen, Debdeep Jena, Huili G. Xing, Shin Mou, David A. Muller, Shun-Li Shang, Zi-Kui Liu, Darrell G. Schlom
Summary: Introduces a growth method called suboxide molecular-beam epitaxy (S-MBE) that significantly enhances the growth rates of Ga2O3 and related materials while maintaining excellent crystalline quality, applicable to a wide range of oxide materials.
Article
Nanoscience & Nanotechnology
Kenny Huynh, Michael E. Liao, Akhil Mauze, Takeki Itoh, Xingxu Yan, James S. Speck, Xiaoqing Pan, Mark S. Goorsky
Summary: The orientational dependence of interfacial reaction between aluminum and different β-Ga2O3 substrates (010, (001), and ((2) over bar 01)) was investigated. It was found that the orientation of β-Ga2O3 substrates influences the formation of aluminum oxide layers and diffusional pathways.
Article
Physics, Applied
Hironori Okumura, Yuji Kato, Takayoshi Oshima, Tomas Palacios
JAPANESE JOURNAL OF APPLIED PHYSICS
(2019)
Article
Physics, Applied
Yuji Kato, Masataka Imura, Yoshiko Nakayama, Masaki Takeguchi, Takayoshi Oshima
APPLIED PHYSICS EXPRESS
(2019)
Article
Physics, Applied
Takayoshi Oshima, Yuji Kato, Eisuke Magome, Eiichi Kobayashi, Kazutoshi Takahashi
JAPANESE JOURNAL OF APPLIED PHYSICS
(2019)
Article
Engineering, Electrical & Electronic
Toshiyuki Oishi, Kosuke Urata, Makoto Hashikawa, Kosuke Ajiro, Takayoshi Oshima
IEEE ELECTRON DEVICE LETTERS
(2019)
Article
Physics, Applied
Yuichi Oshima, Katsuaki Kawara, Takayoshi Oshima, Mitsuru Okigawa, Takashi Shinohe
JAPANESE JOURNAL OF APPLIED PHYSICS
(2020)
Article
Engineering, Electrical & Electronic
Yuichi Oshima, Katsuaki Kawara, Takayoshi Oshima, Mitsuru Okigawa, Takashi Shinohe
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2020)
Article
Physics, Applied
Katsuaki Kawara, Takayoshi Oshima, Mitsuru Okigawa, Takashi Shinohe
APPLIED PHYSICS EXPRESS
(2020)
Article
Physics, Applied
Yuichi Oshima, Katsuaki Kawara, Takayoshi Oshima, Takashi Shinohe
JAPANESE JOURNAL OF APPLIED PHYSICS
(2020)
Article
Chemistry, Multidisciplinary
Laura E. Ratcliff, Takayoshi Oshima, Felix Nippert, Benjamin M. Janzen, Elias Kluth, Rudiger Goldhahn, Martin Feneberg, Piero Mazzolini, Oliver Bierwagen, Charlotte Wouters, Musbah Nofal, Martin Albrecht, Jack E. N. Swallow, Leanne A. H. Jones, Pardeep K. Thakur, Tien-Lin Lee, Curran Kalha, Christoph Schlueter, Tim D. Veal, Joel B. Varley, Markus R. Wagner, Anna Regoutz
Summary: Ga2O3 and its polymorphs have great potential for electronic structure engineering. In this study, a robust atomistic model of gamma-Ga2O3 is developed using density functional theory and machine-learning approach, which is validated by experimental results. This work is of significant importance for understanding the electronic structure of complex, disordered oxides.
ADVANCED MATERIALS
(2022)
Article
Physics, Applied
Takayoshi Oshima, Yuichi Oshima
Summary: Selective area growth of beta-Ga2O3 was demonstrated by HCl-based halide vapor phase epitaxy on SiO2-masked (001) and (010) beta-Ga2O3 substrates. High-aspect-ratio structures with (100) sidewall facets were observed for stripe windows along [010] and [001] directions on the respective substrates. These structures can be applied to trenches and fins for beta-Ga2O3-based power devices.
APPLIED PHYSICS EXPRESS
(2022)
Article
Physics, Applied
Takayoshi Oshima
Summary: In this study, a patterned metal on a beta-Ga2O3 substrate surface was used as an embedded photomask to demonstrate the applicability of backside-exposure lithography to beta-Ga2O3 substrates. Self-aligned photoresist patterning, lift-off, and etching processes were demonstrated for an AZ5214E photoresist in both the positive and negative processing modes. The findings suggest that backside-exposure photolithography is a promising fabrication approach for future beta-Ga2O3-based devices.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Hitoshi Takane, Takayoshi Oshima, Katsuhisa Tanaka, Kentaro Kaneko
Summary: Selective-area growth of r-SnO2 was achieved on a SiO2-masked r-TiO2 (110) substrate. The heteroepitaxy process led to the growth of islands with {100}-, {110}-, and {011}-faceted sidewalls, which matched the equilibrium shape of the rutile structure. Coalescence of the islands formed a flat (110) top surface on the striped window, followed by lateral overgrowth. Cross-sectional transmission-electron-microscopy observation revealed that misfit dislocations propagated perpendicular to the facet planes due to the image force effect, and the dislocation density decreased significantly in the wing regions.
APPLIED PHYSICS EXPRESS
(2023)
Article
Physics, Applied
Takayoshi Oshima, Yuichi Oshima
Summary: We have demonstrated the effectiveness of plasma-free HCl gas etching for fabricating high-aspect-ratio fins/trenches on a SiO2-masked (010) beta-Ga2O3 substrate. The etching process resulted in the formation of holes or trenches with etching-resistant (100)- and ((1) over bar 01)-faceted sidewalls. By etching in the striped windows along [001], we achieved fins and trenches with flat (100)-faceted vertical sidewalls and slightly rough {310}-faceted inclined bottom corners. The vertical-to-horizontal etching ratio was as high as about 11-14. Our findings suggest that HCl etching is a promising method for such fabrication without plasma damage.
APPLIED PHYSICS EXPRESS
(2023)
Article
Physics, Applied
Takayoshi Oshima, Yuichi Oshima
Summary: In this study, SiO2-masked (001) beta-Ga2O3 substrates were dry etched in HCl gas flow at a high temperature without plasma excitation. The etching selectively formed holes or trenches with inner sidewalls of (100) and/or {310} facets, which are planes of lowest surface energy density and oxygen-close-packed slip planes, respectively. The (100) faceted sidewalls were flat and close to the substrate surface normal. This dry etching method shows promise for fabricating plasma-damage-free trenches and fins for beta-Ga2O3-based power devices.
APPLIED PHYSICS LETTERS
(2023)
Article
Nanoscience & Nanotechnology
Yuma Kato, Muneaki Yamamoto, Akiyo Ozawa, Yu Kawaguchi, Akinobu Miyoshi, Takayoshi Oshima, Kazuhiko Maeda, Tomoko Yoshida
E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY
(2018)