Article
Physics, Applied
Hiroyuki Sazawa, Hirotaka Yamaguchi
Summary: We grew a single-domain 3C layer on a step-controlled C-face 4H-SiC substrate to create a 3C/4H-SiC heterostructure. The use of such a substrate demonstrated the effectiveness of growing a thin highly crystalline single-domain 3C layer. The heterostructure displayed an electron Hall mobility of 7224 cm(2)/V s at 32 K, which is significantly higher than previous reports and can be attributed to single-domain formation. The constant sheet carrier density and high mobility in a wide temperature range suggest conduction in a two-dimensional electron gas, highlighting the potential of C-face 3C/4H heterostructures for high electron mobility transistor applications.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Ryotaro Sakakibara, Jianfeng Bao, Keisuke Yuhara, Keita Matsuda, Tomo-o Terasawa, Michiko Kusunoki, Wataru Norimatsu
Summary: We have discovered a step unbunching phenomenon that is the opposite of the step bunching phenomenon. When a 4H-SiC (0001) surface is annealed at a high temperature, steps bunch up due to different velocities of step motion, resulting in steps taller than several nanometers. However, we found that these bunched steps can be unbunched into lower height steps when subsequently annealed at lower temperatures. This competition between energetics and kinetics can explain the underlying mechanism. This finding provides a new method for surface smoothing of SiC using hydrogen etching and has potential implications for SiC power devices and two-dimensional material growth techniques.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Kohei Fukuma, Anton Visikovskiy, Takushi Iimori, Toshio Miyamachi, Fumio Komori, Satoru Tanaka
Summary: Thermal decomposition of vicinal 6H-SiC(0001) surfaces with miscut angles toward the [1 (1) over bar 00] direction leads to the formation of pairs of (0001) macroterraces and (1 (1) over bar 0n) macrofacets covered with graphene. The graphene forms a (6 root 3 x 6 root 3) buffer layer on the macroterraces and generates a pseudographene nanoribbon (pseudo-GNR) array on the macrofacets.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Physics, Condensed Matter
A. Kawasuso, K. Wada, A. Miyashita, M. Maekawa, H. Iwamori, S. Iida, Y. Nagashima
Summary: Two types of positronium were observed on 4H SiC(0001) surfaces, with different energy levels, possibly originating from surface state electrons or conduction electrons.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Materials Science, Coatings & Films
Hsueh- Chen, Kun-An Chiu, Jing-Feng Lin, Kuan-Yu Lin, Wei-Chia Chen, Ping-Hsun Wu, Cheng-Jung Ko, Li Chang, Chun-Hua Chen
Summary: Epitaxial TiN film has been successfully grown on a semi-insulating single crystal SiC substrate. The effects of growth temperature and nitrogen flow ratio on film quality and growth rate were investigated, revealing that increasing the nitrogen flow ratio improves film quality but decreases growth rate.
SURFACE & COATINGS TECHNOLOGY
(2022)
Article
Engineering, Electrical & Electronic
Rui Li, Kaimin Zhang, Yi Zhang, Zhenzhen Zhang, Peixuan Ji, Chengqian Shi, Danni Hao, Yipeng Zhang, Ramiro Moro, Yanqing Ma, Lei Ma
Summary: The study investigated the effects of processing parameters on the hydrogen etching of 4H-SiC (0001) and developed a new two-step etching method with a specifically designed crucible, achieving high efficiency in realizing atomically uniform SiC surface morphology with over 70% coverage of the sample surface.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2022)
Article
Crystallography
Xuejiang Chen, Hao Zhao, Wensen Ai
Summary: The competitive growth process of the 4H and 6H polytypes of SiC was studied using a competitive Kinetic Monte Carlo model, which considers the interaction energy between silicon and carbon atoms. The results show that higher temperature and a larger proportion of silicon source promote the preferential growth of the 6H polytype during competitive growth.
JOURNAL OF CRYSTAL GROWTH
(2021)
Article
Chemistry, Multidisciplinary
Takato Fukui, Yoshinobu Matsuda, Makoto Matsukura, Takahiro Kojima, Mitsuru Funato, Yoichi Kawakami
Summary: GaN layers are grown on Al-pretreated ScAlMgO4 substrates using MOVPE without LT buffer layers. The Al pretreatment results in the nucleation of AlN on ScAlMgO4. The GaN MOVPE inverts the polarity from N-polar to metal polar, leading to better crystalline quality compared with conventional LT-buffer technology.
CRYSTAL GROWTH & DESIGN
(2023)
Review
Chemistry, Multidisciplinary
Ivan Shtepliuk, Filippo Giannazzo, Rositsa Yakimova
Summary: The growth of materials on a dangling-bond-free interface like graphene requires additional surface pre-treatment steps, but epitaxial graphene on SiC might offer better conditions. The study focuses on understanding the growth mechanisms through magnetron sputtering, electrodeposition, and atomic layer deposition, with the hope of contributing to the development of new electronic devices.
APPLIED SCIENCES-BASEL
(2021)
Article
Chemistry, Inorganic & Nuclear
Laurent Souqui, Sachin Sharma, Hans Hogberg, Henrik Pedersen
Summary: This study successfully deposited pure B4C on silicon carbide substrates using chemical vapor deposition, and found that the different surfaces of the substrate have varying abilities to act as carbon sources, affecting the growth mode of the film.
DALTON TRANSACTIONS
(2022)
Article
Chemistry, Physical
Eric Formo, Jordan A. Hachtel, Yassamin Ghafouri, Matthew A. Bloodgood, Tina T. Salguero
Summary: In situ electron microscopy imaging and spectroscopy were used to study the evolution of quasi-1D NbS3-IV nanoribbons, revealing a dramatic transformation into textured configurations and aligned 2H-NbS2 sheets. Atomic resolution imaging and spectroscopy techniques confirmed the chemical changes, leading to a proposed atomistic mechanism for the conversion of NbS3-IV into 2H-NbS2.
CHEMISTRY OF MATERIALS
(2022)
Article
Chemistry, Physical
Yong Han, Marek Kolmer, Michael C. Tringides, James W. Evans
Summary: SiC-supported graphene intercalated by a two-dimensional Pb monolayer is a promising platform for spintronic applications. The thermodynamic stability of this structure has been confirmed in recent experiments. However, the details of intercalated phases, location of atoms, thermodynamic preference, and intercalation pathways are still not fully understood. In this study, extensive density functional theory calculations were conducted to investigate the thermodynamics and kinetics of Pb intercalation on graphene/SiC(0001). The results suggest that intercalation of complete Pb layers in the gallery is strongly favored over other configurations, and more complex intercalation pathways are involved.
Article
Chemistry, Physical
Takashi Yamada, Takenori Tawa, Natsumi Murase, Hiroyuki S. Kato
Summary: The formation of a wetting layer of water on a graphite surface was investigated. It was found that an extended ice network is formed on graphite, different from that on metal surfaces. Graphite is hydrophobic under ambient conditions, but it is considered inherently hydrophilic for a clean surface.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Physics, Condensed Matter
Jichao Hu, Dan Li, Xiaomin He, Xi Wang, Bei Xu, Yuan Zang, Lianbi Li
Summary: CuAlO2 films were prepared on 4H-SiC substrates using the sol-gel method, with a homogeneous distribution of crystal grains observed on the surface. The films were predominantly composed of CuAlO2 and CuAl2O4 phases, exhibiting stable optical bandgaps and multiple emission peaks. The fabricated heterojunction diode showed typical rectification behavior, indicating potential for high injection capacity SiC bipolar devices.
SUPERLATTICES AND MICROSTRUCTURES
(2021)
Article
Materials Science, Multidisciplinary
Kun-An Chiu, Jing-Feng Lin, Kuan-Yu Lin, Ping-Hsun Wu, Hsueh- Chen, Cheng-Jung Ko, Chun-Hua Chen, Li Chang
Summary: Heteroepitaxial TiC films were grown on 4H-SiC substrates using DC magnetron reactive sputtering with CH4 flux ratio in Ar as the variable. The film quality was analyzed using XRD and TEM techniques, which showed that the TiC films were heteroepitaxially grown on 4H-SiC substrates with a specific relationship. The film exhibited a minimum FWHM value and desirable resistivity when deposited at 700°C with a 4% CH4 flow ratio.
Article
Materials Science, Multidisciplinary
Yao Zhang, Yuefeng Yin, Guy Dubuis, Tane Butler, Nikhil V. Medhekar, Simon Granville
Summary: In this study, thin films of Weyl semimetal Co2MnGa are demonstrated to exhibit a large anomalous Hall angle at both low temperature and room temperature, making them promising for room temperature topo-spintronics applications. However, a significant decrease in the anomalous Hall angle is observed with decreasing thickness.
NPJ QUANTUM MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Sayantan Ghosh, Abin Varghese, Himani Jawa, Yuefeng Yin, Nikhil Medhekar, Saurabh Lodha
Summary: This study explores the use of WSe2/SnSe2 type-III structures in photodetectors, showing high negative responsivity and fast response time with controllable photocurrent polarity. By adjusting the band alignment from type-II to type-III, a significant enhancement in responsivity can be achieved, further supported by density functional theory calculations.
Article
Chemistry, Multidisciplinary
Qingdong Lin, Stefano Bernardi, Babar Shabbir, Qingdong Ou, Mingchao Wang, Wenping Yin, Shiqi Liu, Anthony S. R. Chesman, Sebastian O. Furer, Guangyuan Si, Nikhil Medhekar, Jacek Jasieniak, Asaph Widmer-Cooper, Wenxin Mao, Udo Bach
Summary: This study demonstrates a method for controlling the crystallization of inorganic cesium lead halide perovskite microstructures, successfully tuning the structure of perovskite crystals from 0D to 2D to 3D by adjusting the water to dimethylsulfoxide ratios.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Physical
Zhuoxin Li, Xing Li, Mingchao Wang, Molang Cai, Xiaoqiang Shi, Yaqi Mo, Xianggang Chen, Dongxu Ren, Miao Yang, Xuepeng Liu, Rui Jia, Nikhil Medhekar, Songyuan Dai
Summary: By introducing ammonium thiocyanate as a bifunctional additive into the precursor solution, the conversion efficiency and stability of tin-based perovskite solar cells were significantly improved in this study, with the PCE increasing from 4.45% to 8.15%. The modified perovskite film exhibited better film quality and superior environmental stability.
ACS APPLIED ENERGY MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Himani Jawa, Abin Varghese, Sayantan Ghosh, Srilagna Sahoo, Yuefeng Yin, Nikhil Medhekar, Saurabh Lodha
Summary: This report demonstrates visible-to-near infrared wavelength-driven negative photoconductance (NPC) and positive photoconductance (PPC), along with reversible switching between the two. A few layer MoS2 flake covered on a broadband black phosphorus field effect transistor is used to achieve this, with the crossover switching wavelength and photoresponsivities modulated by varying the MoS2 bandgap through its flake thickness and electrostatic gating.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Qile Li, Chi Xuan Trang, Weikang Wu, Jinwoong Hwang, David Cortie, Nikhil Medhekar, Sung-Kwan Mo, Shengyuan A. Yang, Mark T. Edmonds
Summary: Combining magnetism and nontrivial band topology can achieve the quantum anomalous Hall (QAH) effect at high temperatures for lossless transport applications. In this study, a heterostructure consisting of two single-septuple layers (1SL) of MnBi2Te4, an ultrathin few quintuple layer (QL) Bi2Te3, and another 1SL MnBi2Te4 was grown via molecular beam epitaxy. The electronic structure was probed using angle-resolved photoelectron spectroscopy, and strong hexagonally warped massive Dirac fermions and a bandgap of 75 +/- 15 meV were observed. The magnetic origin of the gap was confirmed, and these findings provide insights into magnetic proximity effects in topological insulators and a promising platform for realizing the QAH effect at elevated temperatures.
ADVANCED MATERIALS
(2022)
Article
Chemistry, Physical
Tao Jiang, Hao Min, Renmeng Zou, Mingchao Wang, Kaichuan Wen, Jingya Lai, Lei Xu, Ying Wang, Wenjie Xu, Chengcheng Wang, Kang Wei, Nikhil Medhekar, Qiming Peng, Jin Chang, Wei Huang, Jianpu Wang
Summary: The dipole moment of the bulky cation is found to be an important factor controlling the distribution and crystallinity of different quantum wells in quasi-2D perovskites. Bulky cations with moderate dipole moment can lead to moderately distributed well-width MQWs and achieve favorable optical and electronic properties, resulting in improved device efficiency.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Abin Varghese, Yuefeng Yin, Mingchao Wang, Saurabh Lodha, Nikhil Medhekar
Summary: By conjugating with low-dimensional materials, such as transition metal dichalcogenides, ultrathin 2D perovskites can be extended to various visible-range photophysical applications. The bandgaps, carrier effective masses, and band offsets can be widely tuned to achieve effective separation of photogenerated excitons, enhancing the performance of photodetection and photovoltaic applications.
ADVANCED MATERIALS INTERFACES
(2022)
Article
Materials Science, Multidisciplinary
Chen-Chen Er, Lutfi K. Putri, Boon-Junn Ng, Jie-Yinn Tang, Nikhil V. Medhekar, Siang-Piao Chai
Summary: Controlling the product selectivity of CO2 photoreduction through allotropism is a promising strategy. In this study, three phosphorus allotropes were modeled as CO2 reduction photocatalysts and their CO2 adsorption behavior was investigated. It was found that each allotrope exhibits different selectivity towards C1 products due to their distinct p-band centers.
MATERIALS TODAY PHYSICS
(2022)
Article
Chemistry, Physical
Mingchao Wang, Han Ye, Vallabh Vasudevan, Nikhil Medhekar
Summary: This study investigates the thermodynamic and electrochemical performance of layered material MoS2 as a cathode for Mg-ion batteries using first-principles calculations. The findings show that increasing the interlayer spacing can enhance Mg diffusivities and specific capacity, but reduce electrode voltages.
JOURNAL OF POWER SOURCES
(2022)
Article
Physics, Applied
Chen-Chen Er, Lutfi K. Putri, Nikhil Medhekar, Siang-Piao Chai
Summary: Enhancement of carbon nitride through single transition metal atom modification improves its photocatalytic performance, with Pd and Cu identified as the most promising candidates for CO2 reduction.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
Bernard Field, Agustin Schiffrin, Nikhil Medhekar
Summary: This study demonstrates how substrates influence the magnetic phases in kagome MOFs, taking into account factors such as MOF-substrate coupling, MOF-substrate charge transfer, strain, and external electric fields. The findings provide useful predictions for studying tunable interaction-induced magnetism in surface-supported 2D (metal-)organic materials.
NPJ COMPUTATIONAL MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Shenghan Su, Laure Bourgeois, Nikhil V. Medhekar
Summary: The high strength of structural aluminium alloys is due to the controlled precipitation of specific intermetallic phases. In this study, we investigate the AlPt system and design a workflow to predict the thermodynamics of various phases and their precipitation sequence in binary alloying systems. Our findings suggest that Al2Pt will precipitate first and form bulk-like interfaces similar to Al2Au rather than Al2Cu.
Article
Chemistry, Multidisciplinary
Motomi Aoki, Yuefeng Yin, Simon Granville, Yao Zhang, Nikhil V. Medhekar, Livio Leiva, Ryo Ohshima, Yuichiro Ando, Masashi Shiraishi
Summary: Co2MnGa, a topological quantum material with high structural symmetry, exhibits a gigantic anisotropy of self-induced spin-orbital torque (SOT), which is a result of the interplay between the topological nature of the electronic states and external strain.
Article
Materials Science, Multidisciplinary
Yuefeng Yin, Chutian Wang, Michael S. Fuhrer, Nikhil Medhekar
Summary: Tuning the interaction between the bulk and edge states of topological materials is a powerful tool for manipulating edge transport behavior in planar bismuthene. By exploring the impact of various perturbation effects, such as device size, substrate potentials, and applied transverse electric field, the electronic structure and edge transport in planar bismuthene can be engineered to exhibit either a gapped or conducting unconventional helical spin texture. These results open up new directions for discovering novel spin transport patterns in topological materials and provide critical insights for the fabrication of topological spintronic devices.
MATERIALS TODAY PHYSICS
(2023)