Article
Chemistry, Physical
Zhihan Hu, Di Chen, SeungSu Kim, Rijul Chauhan, Yongchang Li, Lin Shao
Summary: The effect of stress on irradiation responses of highly oriented pyrolytic graphite (HOPG) was studied using molecular dynamics simulation, proton irradiation, and Raman characterization. The results showed that stress reduces the average threshold displacement energy, increases the damage peak and the number of surviving defects, and induces local cleavage. Experimental results also confirmed the enhanced irradiation effect caused by stress.
Article
Chemistry, Analytical
Cesar G. Gomez, Omar E. Linarez Perez, Lucia B. Avalle, Mariana I. Rojas
Summary: This study presents a comprehensive analysis of the morphology and electrochemical properties of graphite carbon nitride/highly oriented pyrolytic graphite electrode surface for hydrogen peroxide reduction reaction. Results indicate that graphite carbon nitride is a valuable electroactive material that can enhance the electro-activity of other cheaper carbonaceous substrates.
JOURNAL OF ELECTROANALYTICAL CHEMISTRY
(2021)
Article
Materials Science, Multidisciplinary
Hansong Wu, Jiaxin Song, Shanling Wang, Jiqiu Wen, Aiqun Gu, Yixin Dai, Wenkang Li, Hong Zhang, Filippo S. Boi
Summary: This study investigates the structural properties and possible magnetic effects of graphite samples with coexistence of rhombohedral-stacking and hexagonal moire-superlattices. The results show a significant weakening of the rhombohedral-component in thin samples, while the coexistence of hexagonal moire-superlattices with rhombohedral domains is observed in thick samples. Magnetic characterization reveals an unusual enhancement of diamagnetic susceptibility from T similar to 300 K to T similar to 2 K, possibly resulting from a disclination-free structural configuration.
MATERIALS TODAY COMMUNICATIONS
(2022)
Article
Materials Science, Multidisciplinary
Hansong Wu, Jiaxin Song, Shanling Wang, Jiqiu Wen, Aiqun Gu, Yixin Dai, Wenkang Li, Hong Zhang, Filippo S. Boi
Summary: The study investigated the structural properties of HOPG materials, discovering the coexistence of hexagonal and rhombohedral stacking with possible magnetic effects. Large-area hexagonal moire superlattices were found in exfoliated samples, with a weakening of the rhombohedral component in thin samples. The unusual magnetic overlay and spin-glass-like behavior were identified, indicating variations in the structural configuration and non-monotonic X-ray rocking-curve distribution.
MATERIALS TODAY COMMUNICATIONS
(2022)
Article
Green & Sustainable Science & Technology
Marcos A. Bento, Sara Realista, Ana S. Viana, Ana M. Ferraria, Paulo N. Martinho
Summary: Reproducible materials with detection properties towards specific molecules are crucial for device fabrication. Highly oriented pyrolytic graphite and cryptand molecules play important roles in sensing certain analytes with high selectivity through functionalization. The thickness and structure of the final layers are influenced by different functionalization methods.
Article
Chemistry, Multidisciplinary
Andreas K. Freund, Hao Qu, Xiang Liu, Mike Crosby, Changyong Chen
Summary: This article reviews the neutron diffraction properties of highly oriented pyrolytic graphite (HOPG) by using experimental results and diffraction theory. The analysis shows that a detailed X-ray diffraction study can be useful in optimizing the efficiency of composite neutron monochromators and analyzers.
JOURNAL OF APPLIED CRYSTALLOGRAPHY
(2022)
Article
Materials Science, Multidisciplinary
Andrew McEllistrim, Aitor Garcia-Ruiz, Zachary A. H. Goodwin, Vladimir I. Fal'ko
Summary: Tetralayer graphene, a new member of few-layer graphenes, demonstrates versatile electronic properties. Spectroscopic characteristics, such as angle-resolved photoemission spectroscopy, dynamical optical conductivity, and Raman spectra, can be used to identify the stacking order of tetralayer graphene films in a noninvasive manner.
Article
Chemistry, Physical
Mariana I. Rojas, Danna Villca Centellas, Omar E. Linarez Perez, Lucia B. Avalle
Summary: By using electrochemical impedance spectroscopy (EIS), the change in capacitive response of the highly oriented pyrolytic graphite (HOPG)/electrolyte interface due to the presence of a non-compact indole film adsorbed on the electrode surface was detected. Atomistic simulations were performed to understand the adsorption phenomenon, showing that the adsorption of indole on functionalized armchair-edge steps begins with hydrogen bond interaction and then continues over terraces and surface defects, forming an ordered film. The presence of the film on surface modifies the surface electronic structure due to partial charge transfer related to the adsorption process. Knowledge of indole adsorption on HOPG is important for improving sensor design.
Article
Chemistry, Multidisciplinary
Haoyu Zhu, Joshua A. Russell, Zongtang Fang, Pete Barnes, Lan Li, Corey M. Efaw, Allison Muenzer, Jeremy May, Kailash Hamal, I. Francis Cheng, Paul H. Davis, Eric J. Dufek, Hui Xiong
Summary: The study focuses on the formation and evolution of SEI on graphitic electrodes, revealing the important influence of electrolyte choice and electrode surface properties on the chemical composition and morphology of SEI. Furthermore, the research suggests that introducing structural defects into graphitic electrodes can improve their electrochemical performance and provides guidance for designing functional SEIs.
Article
Chemistry, Multidisciplinary
Qingwei Yan, Jingyao Gao, Ding Chen, Peidi Tao, Lu Chen, Junfeng Ying, Xue Tan, Le Lv, Wen Dai, Fakhr E. Alam, Jinhong Yu, Yuezhong Wang, He Li, Chen Xue, Kazuhito Nishimura, Sudong Wu, Nan Jiang, Cheng-Te Lin
Summary: The mesoplasma chemical vapor deposition (CVD) technology was used to synthesize vertically aligned graphene nanowalls (GNWs) and achieve high thermal conductivity polymer composites with low filler loadings.
Article
Chemistry, Organic
Jimmy Richard, Jean Joseph, Can Wang, Artur Ciesielski, Jean Weiss, Paolo Samori, Victor Mamane, Jennifer A. Wytko
Summary: Commercial 4,4'-bipyridine is commonly used as a linker in 3D self-assembled architectures and as a connector in 2D networks. Alkyl substituents on the bipyridine skeleton play a crucial role in forming 2D self-assembled patterns on surfaces. Different supramolecular patterns at the graphite-solution interface are primarily influenced by the nature and position of the alkyl chains.
JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Chemistry, Physical
Lu'an Guo, Yitao Wang, Dogan Kaya, Zhiming Wang, Min Zhang, Quanmin Guo
Summary: Researchers successfully built a C-60-C-70 organic molecular heterojunction on the HOPG surface using layer-by-layer growth method. C-70 molecules assemble into a close-packed second layer matched to the underlying C-60 layer, showcasing unique physical properties and functionality.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Physical
A. Krautsou, O. N. Shornikova, A. I. Bulygina, A. B. Solopov, A. L. Kustov, V. V. Avdeev
Summary: Graphite intercalated compounds (GICs) with different stage numbers were prepared and studied. By examining the correlation between the graphite oxidation depth and the pore structure parameters, a strong relationship between the two was revealed.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Zejun Zhang, Yizhou Yang, Jihong Wang, Yuying Zhou, Zhongqi Ren, Ni Zhong, Chungang Duan, Ying Wang, Long Yan, Haiping Fang
Summary: A novel method for preparing ultra-thin NaNO3 flakes on HOPG surface mediated by water was reported, with adjustable electrical conductivity. The findings offer a new way to obtain thin films of inorganic salts.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Multidisciplinary
Ken Suzuki, Ryohei Nakagawa, Qinqiang Zhang, Hideo Miura
Summary: In this study, a basic design of area-arrayed graphene nanoribbon (GNR) strain sensors was proposed. GNRs with widths of 200 nm and above were found to be metallic conductors, while 50 nm GNRs exhibited high sensitivity. A four-point bending test revealed that the gauge factor of the 50 nm GNR was about 50, making it suitable for highly sensitive strain sensors.
Article
Physics, Applied
Hajime Tanaka, Tsunenobu Kimoto, Nobuya Mori
APPLIED PHYSICS EXPRESS
(2020)
Article
Physics, Applied
Futo Hashimoto, Nobuya Mori
Summary: In this study, intra-layer band-to-band tunneling transmission functions of monolayer transition metal dichalcogenides were calculated using the non-equilibrium Green function method combined with the tight-binding approximation. The differences in transmission functions between nanosheet and nanoribbon structures were explored, as well as the material dependence for various transition metal dichalcogenides. It was found that the nanoribbon structure exhibited lower transmission functions compared to the nanosheet structure, attributed to indirect transitions and small spatial overlap of wave functions at the conduction band and valence band edges. Additionally, material-dependent variations in transmission functions were related to tunneling mass and bandgap energy in nanosheet structures.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Jo Okada, Futo Hashimoto, Nobuya Mori
Summary: The research proposes an equivalent model suitable for computer programs, capable of accurately reproducing the transport window of target band structures. By implementing automatic differentiation techniques on a machine learning platform, successful simulations and tests were conducted on semiconductor nanostructures.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Hiroshi Tabata, Hiroaki Matsuyama, Taishi Goto, Osamu Kubo, Mitsuhiro Katayama
Summary: Some gas sensors exhibit enhanced sensitivity and response rates under light illumination, with molybdenum disulfide (MoS2) thin layers showing effective photoactivated gas responses to visible light. The photoactivated response is mainly attributed to the photovoltaic effect, with the sensor response depending on the Langmuir adsorption isotherm of NO2 molecules on the MoS2 layer. The fast response/recovery of the photoactivated response is linked to carrier mobility modulation of MoS2 due to dipole scattering of adsorbed NO2 molecules.
Article
Physics, Applied
Jo Okada, Futo Hashimoto, Nobuya Mori
Summary: The researchers have proposed an equivalent model for simulating tunnel devices, which reproduces both real and complex band-structures of the target system. This model enables a reduction in Hamiltonian matrix size, leading to faster quantum transport simulations of tunnel devices.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Nanoscience & Nanotechnology
N. Mori, A. Komada, G. Mil'nikov
Summary: The thermal conductance of one-dimensional mass-disordered systems is calculated using linear and quadratic dispersion models. Different dispersion models exhibit different thermal diffusion behaviors, with super-diffusive nature for the linear model and normal-diffusion behavior for the quadratic model.
Article
Physics, Applied
Nobuya Mori, Futo Hashimoto, Takaya Mishima, Hajime Tanaka
Summary: The analytical formula for the transmission function of inter-layer intra-band tunneling in coupled narrow two-dimensional materials is derived, and analytical models for the intra-band tunneling conductance G, the transmission function of inter-layer band-to-band tunneling, and the maximum band-to-band tunneling current I (max) are obtained. It is found that G and I (max) exhibit different characteristics depending on the channel length.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
H. Tanaka, T. Kimoto, N. Mori
Summary: This study computationally analyzes the effects of band structures and scattering rates on the high-field carrier transport properties in wide-bandgap semiconductors. The study reveals that the average of the group velocity and the width of the Brillouin zone are crucial factors that determine the impact ionization coefficients.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Wataru Miyazaki, Hajime Tanaka, Nobuya Mori
Summary: The effects of strain on the band structure of GaN were investigated using an empirical tight-binding method. The impacts on its bandgap, carrier effective mass, and group velocity were discussed. The cause of the variation of the band structure, including effective-mass exchange, was discussed by analyzing the orbital components at the top of the valence band. Analysis of the average group velocity showed that tensile uniaxial or compressive biaxial strain may be beneficial for achieving higher breakdown voltage in vertical GaN devices due to the smaller group velocity of the valence band. Similarly, higher breakdown voltages were predicted for horizontal devices due to tensile biaxial strain.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Jo Okada, Nobuya Mori, Gennady Mil'nikov
Summary: The accuracy of the equivalent model (EM) in the band-to-band tunneling simulation of semiconductor nanowires is investigated. The EM accurately reproduces both the traveling states and the evanescent states as the target window is widened. The relative error of the maximum tunnel current decreases exponentially with the transport window size. It is also found that semiconductor nanowires can be classified into D-type and I-type based on the dispersion of the evanescent mode, and D-type nanowires can be represented with a smaller EM basis size or higher accuracy compared to I-type nanowires.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Yutoku Murakami, Sachika Nagamizo, Hajime Tanaka, Nobuya Mori
Summary: The tunneling current in heavily doped 4H-SiC Schottky barrier diodes under reverse-biased conditions is accurately calculated by considering the non-parabolicity of the complex bands using the empirical pseudopotential method. The approximation assuming a parabolic complex band underestimates the experimental tunneling current, whereas our proposed non-parabolic complex band calculation reproduces the experimental results more accurately. These findings highlight the importance of considering the non-parabolicity of complex bands in accurately calculating the tunneling current.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Kazunori Matsuda, Masashi Yamamoto, Michio Mikawa, Shiro Nagaoka, Nobuya Mori, Kazuo Tsutsui
Summary: The effects of hydrogen radical treatment on the piezoresistance coefficients of germanium under uniaxial stress were investigated. It was found that the treatment caused a dramatic change in the gauge factor and majority carrier of non-doped germanium. The results suggest that the piezoresistance coefficients of germanium are influenced by vacancy-related levels around the midgap, which act as donors or acceptors depending on the Fermi level and are passivated by hydrogen radicals.
APPLIED PHYSICS EXPRESS
(2023)
Article
Physics, Applied
Yuya Furusawa, Osamu Kubo, Riku Yamamoto, Yudai Suzuki, Naoki Matsuura, Yuuki Hiraoka, Hiroshi Tabata, Mitsuhiro Katayama
Summary: Germanane, a layered material with single-layer germanium terminated by hydrogen, was used as the channel material in back-gate-type FETs. Titanium, aluminum, and nickel served as the source and drain electrodes, and most of the fabricated FETs exhibited ambipolar characteristics. Among the three electrode materials, nickel showed the highest field-effect carrier mobility. It was observed that the mobility followed a T (-3/2) law below 273 K, but deviated from this law above 293 K.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
Gennady Mil'nikov, Jun-ichi Iwata, Nobuya Mori, Atsushi Oshiyama
Summary: The paper presents a device simulator that can calculate transport characteristics from first principles. The program can efficiently perform large-scale parallel calculation of quantum transport in nanoscale devices with thousands of atoms, based on the real-space Kohn-Sham Hamiltonian and improved numerical algorithms. Several computational improvements have been introduced in constructing a reduced quantum transport model and implementing the R-matrix computational scheme in NEGF simulations.
JOURNAL OF COMPUTATIONAL ELECTRONICS
(2023)
Article
Materials Science, Multidisciplinary
Osamu Kubo, Seijiro Kinoshita, Hitoshi Sato, Koji Miyamoto, Ryuji Sugahara, Satoshi Endo, Hiroshi Tabata, Taichi Okuda, Mitsuhiro Katayama
Summary: The structure of Al(111)3x3-Ge was found to consist of a unit cell with 10 Ge atoms, similar to silicene rather than the previously reported honeycomb lattice. The band structure of Al(111)3x3-Ge was investigated and the model proposed based on density functional theory well reproduced the ARPES spectra, indicating a kagome-like structure.