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Toward Perfect Surfaces of Transition Metal Dichalcogenides with Ion Bombardment and Annealing Treatment

ACS Applied materials and Interfaces 2023年第12期15卷 16153-16161页

作者： Chen, Wan-Hsin Kawakami, Naoya Hsueh, Jing-Wen Kuo, Lai-Hsiang Chen, Jiun-Yu Liao, Ting-Wei Kuo, Chia-Nung Lue, Chin-Shan Lai, Yu-Ling Hsu, Yao-Jane Lien, Der-Hsien Hu, Chenming Chou, Jyh-Pin Luo, Meng-Fan Lin, Chun-Liang Department of Electrophysics National Yang Ming Chiao Tung University Hsinchu300 Taiwan Department of Physics National Central University Jhongli320 Taiwan Department of Physics National Cheng Kung University Tainan701 Taiwan Taiwan Consortium of Emergent Crystalline Materials National Science and Technology Council Taipei106 Taiwan Program on Key Materials Academy of Innovative Semiconductor and Sustainable Manufacturing National Cheng Kung University Tainan701 Taiwan Nanoscience Group National Synchrotron Radiation Research Center Hsinchu300 Taiwan Institute of Electronic Engineering National Yang Ming Chiao Tung University Hsinchu300 Taiwan International College of Semiconductor Technology National Yang Ming Chiao Tung University Hsinchu300 Taiwan Department of Physics National Changhua University of Education Changhua500 Taiwan

Layered transition metal dichalcogenides (TMDs) are two-dimensional materials exhibiting a variety of unique features with great potential for electronic and optoelectronic applications. The performance of devices fabricated with mono or few-layer TMD materials, nevertheless, is significantly affected by surface defects in the TMD materials. Recent efforts have been focused on delicate control of growth conditions to reduce the defect density, whereas the preparation of a defect-free surface remains challenging. Here, we show a counterintuitive approach to decrease surface defects on layered TMDs: a two-step process including Ar ion bombardment and subsequent annealing. With this approach, the defects, mainly Te vacancies, on the as-cleaved PtTe2 and PdTe2 surfaces were decreased by more than 99%, giving a defect density 10 cm-2, which cannot be achieved solely with annealing. We also attempt to propose a mechanism behind the processes. © 2023 American Chemical Society.

关键词： Scanning tunneling microscopy

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Ronchigram Simulation and Aberration Correction Training Using ***

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Microscopy Today 2022年第5期30卷 40-43页

作者： Sung, Suk Hyun Schnitzer, Noah Millsaps, William Kourkoutis, Lena F Hovden, Robert Department of Materials Science and Engineering University of Michigan Ann Arbor MI 48109 Department of Materials Science and Engineering Cornell University Ithaca NY 14853 Engineering Physics Program University of Michigan Ann Arbor MI 48109 School of Applied and Engineering Physics Cornell University Ithaca NY 14853 Kavli Institute at Cornell for Nanoscale Science Cornell University Ithaca NY 14853

This article introduces a training simulator for electron beam alignment using Ronchigrams. The interactive web application,***, is an advanced educational tool aimed at making scanning transmission electron microscopy (STEM) more accessible and open. For experienced microscopists, the tool offers on-hand quantification of simulated Ronchigrams and their resolution limits.

关键词： Ronchigram scanning transmission electron microscopy aberration correction image simulation software

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Alternating Cu segregation and its stabilization mechanism for coherent η' precipitates in Al–Zn–Mg–Cu alloys

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materials Today Advances 2024年 23卷

作者： Chiu, Yu-ning Chung, Tsai-fu Yen, Shao-yu Yu, Chung-yi Lin, Wei-ting Hsieh, Chia-chia Lin, Shih-kang Department of Materials Science and Engineering National Cheng Kung University Tainan70101 Taiwan Department of Materials Science and Engineering National Yang Ming Chiao Tung University Hsinchu30010 Taiwan Aluminum Prod R&D Section New Materials R&D Department Kaohsiung81233 Taiwan Research Center National Cheng Kung University Tainan70101 Taiwan Program on Smart and Sustainable Manufacturing Academy of Innovative Semiconductor and Sustainable Manufacturing National Cheng Kung University Tainan70101 Taiwan Core Facility Center National Cheng Kung University Tainan70101 Taiwan

The 7000 series (Al–Zn–Mg) Al-alloys are renowned for their exceptional "lightweight-high strength" properties, primarily owing to nano-sized meta-stable η′ precipitate as the main strengthening phase. However, these η′ precipitates are susceptible to transforming into the stable η2 phase at elevated temperatures, resulting in a decline in strength. To mitigate this, Cu-segregation has been long proposed as a promising method for stabilizing these meta-stable precipitates. However, the mechanisms involved have not been fully understood. In this study, we conducted a thorough investigation on the structural and energetic changes between Cu-free and Cu-segregated η' and η2 precipitates. Utilizing DFT calculations and HAADF-STEM characterizations, we uncovered a distinctive alternating Cu-segregation pattern. This pattern induces significant structural modifications within the bulk of η' precipitates and at the precipitate-matrix interface, markedly enhancing their interfacial and bulk energetics. We believe these modifications are the key factor in improving precipitate stability. Based on our findings, the underlying mechanism of solute segregation was elucidated and a novel strategy for optimal design of Al–Zn–Mg alloys was proposed. © 2024 The Authors

关键词： High strength alloys

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The Effects of Growth Environments on Ws2 in Electrocatalytic Hydrogen Evolution Reaction

SSRN

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SSRN 2023年

作者： Chang, Yung-Huang Huang, Chien-Sheng Chen, Yuan-Tsung Bachelor Program in Industrial Technology National Yunlin University of Science and Technology Yunlin Taiwan Department of Electronic Engineering National Yunlin University of Science and Technology Yunlin Taiwan Graduate School of Materials Science National Yunlin University of Science and Technology Yunlin Taiwan

Transition metal dichalcogenides (TMDs) recently have attracted much attention because of their outstanding catalytic activity, low cost, and earth abundance in the hydrogen evolution reaction (HER). Among these TMDs, MoS2 and WS2 are recognized as promising HER electrocatalysts and have been explored to be one of the candidates for replacing precious metals. In this work, the electrocatalytic activity of WS2 grown in Ar-only, Ar + H2, and ambient environments were studied, where the WS2 was synthesized by thermolysis from (NH4)2WS4 precursor. Different surface morphologies are shown under the different growth atmospheres. The structures of pure WS2, WS2 and WO3 mixed, and almost WO3 grow under the growth atmospheres of Ar-only, Ar + H2, and ambient environment, respectively. All the materials prepared in these different environments exhibit high crystalline characteristic. Especially, the pure WS2 grown in an Ar-only environment presents the preferred (103) lattice plane. The pure WS2 performs the best H2 evolution efficiency, indicating that high crystallinity and preferred (103) lattice plane are relative to the electrocatalytic activity. The studies provide fundamental insight for further design and preparation of electrocatalysts, useful in the development of clean energy. © 2023, The Authors. All rights reserved.

关键词： Electrocatalysts

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Mechanical and radiation shielding properties of Philippine natural zeolite-mixed concrete

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Radiation Physics and Chemistry 2025年 236卷

作者： Rosero, Maria Cecilia SB. Grande, Marianna Lourdes Marie L. Inocencio, Eric M. Gili, Mon Bryan Z. Department of Physical Sciences and Mathematics – University of the Philippines Manila Ermita Manila1000 Philippines Department of Science and Technology – Philippine Nuclear Research Institute Commonwealth Avenue Diliman Quezon City1101 Philippines Medical Imaging Department Las Piñas General Hospital and Satellite Trauma Center Las Piñas City1742 Philippines Materials Science and Engineering Program College of Science University of the Philippines Diliman Diliman Quezon City1101 Philippines

This study investigated the mechanical and radiation shielding properties of Philippine natural zeolite (PNZ)-mixed concrete as a potential sustainable alternative to traditional cement in radiation shielding applications. Concrete mixtures with 0 %, 20 %, and 40 % PNZ replacement were tested for compressive strength, split tensile strength, and radiation shielding efficiency against X-ray and gamma radiation. The specific density of the control sample (pure concrete) is 1.75 g/cm3 while the concrete with 20 % and 40 % cement replacements were 1.62 and 1.61 g/cm3, respectively. Results showed that the 40 % PNZ mixture exhibited the highest mechanical strength, with a 400 % increase in the average compressive strength from the pure concrete mixture, attributed to the pozzolanic reaction between zeolite and calcium hydroxide. The 20 % PNZ mixture demonstrated the best radiation shielding performance, achieving the highest linear attenuation coefficients of 0.623, 0.433, 0.421, and 0.167 cm−1 at 65, 100, 118, and 662 keV, respectively. As a result, the concrete with 20 % cement replacement also exhibited the highest mass attenuation coefficients at these energies. The total atomic cross-section followed the trend 0 % > 20 % > 40 %, with the control sample having the lowest mean free path (MFP) and half-value layer (HVL) at lower energies. Experimental and simulation results confirmed that the 20 % PNZ mixture offers an optimal balance between mechanical strength and radiation shielding while promoting sustainability by reducing cement usage. © 2025 Elsevier Ltd

关键词： Reactor shielding

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Ubiquitous Flat Bands in a Cr-based Kagome Superconductor

arXiv

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arXiv 2024年

作者： Guo, Yucheng Wang, Zehao Xie, Fang Huang, Yuefei Gao, Bin Oh, Ji Seop Wu, Han Liu, Zhaoyu Ren, Zheng Fang, Yuan Biswas, Ananya Zhang, Yichen Yue, Ziqin Hu, Cheng Jozwiak, Chris Bostwick, Aaron Rotenberg, Eli Hashimoto, Makoto Lu, Donghui Kono, Junichiro Chu, Jiun-Haw Yakobson, Boris I. Birgeneau, Robert J. Si, Qimiao Dai, Pengcheng Yi, Ming Department of Physics and Astronomy Rice University HoustonTX77005 United States Advanced Light Source Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States Department of Physics University of California BerkeleyCA94720 United States Department of Physics University of Washington Washington98105 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory Menlo ParkCA94025 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

In the quest for novel quantum states driven by topology and correlation, kagome lattice materials have garnered significant interest due to their distinctive electronic band structures, featuring flat bands (FBs) arising from the quantum destructive interference of the electronic wave function. The tuning of the FBs to the chemical potential would lead to the possibility of liberating electronic instabilities that lead to emergent electronic orders. Despite extensive studies, direct evidence of FBs tuned to the chemical potential and their participation in emergent electronic orders have been lacking in bulk quantum materials. Here using a combination of Angle-Resolved Photoemission Spectroscopy (ARPES) and Density Functional Theory (DFT), we reveal that the low-energy electronic structure of the recently discovered Cr-based kagome metal superconductor CsCr3Sb5 is dominated by a pervasive FB in close proximity to, and below the Fermi level. A comparative analysis with orbital-projected DFT and polarization dependence measurement uncovers that an orbital-selective renormalization mechanism is needed to reconcile the discrepancy with the DFT calculations, which predict the FB to appear 200 meV above the Fermi level. Furthermore, we observe the FB to shift away from the Fermi level by 20 meV in the low-temperature density wave-ordered phase, highlighting the role of the FB in the emergent electronic order. Our results reveal CsCr3Sb5 to stand out as a promising platform for further exploration into the effects of FBs near the Fermi level on kagome lattices, and their role in emergent orders in bulk quantum materials. © 2024, CC BY.

关键词： Density functional theory

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Ultra-thin Carbon Biphenylene Network as an Anisotropic Thermoelectric Material with High Temperature Stability Under Mechanical Strain

arXiv

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arXiv 2024年

作者： Sargın, Gözde Özbal Demirci, Salih Gong, Kai Özçelik, V. Ongun Faculty of Engineering and Natural Sciences Sabanci University Istanbul34956 Turkey Department of Physics Kırıkkale University Kırıkkale71450 Turkey Department of Civil and Environmental Engineering Rice University TX77005 United States Materials Science and Nano Engineering Program Sabanci University Istanbul34956 Turkey

Carbon biphenylene network (C-BPN), which is an ultra-thin material consisting of carbon atoms arranged in square-hexagonal-octagonal (4-6-8) periodic rings, has intriguing properties for nano-scale device design due to its unique crystal structure. Here, using the Landauer formalism in combination with first-principles calculations, we show that C-BPN is a highly stable thermoelectric material at elevated temperatures under mechanical strain, where its thermoelectric efficiency can be anisotropically engineered. Transport calculations reveal that C-BPN’s transmission spectrum has significant degrees of directional anisotropy and it undergoes a metal-insulator transition under strain, which leads to an increase in its Seebeck coefficient. C-BPN’s lattice thermal conductance can be selectively tuned up to 35% bidirectionally at room temperature by strain engineering. Enhancement in its power factor and the suppression of its lattice thermal conductance improves the p-type figure of merit up to 0.31 and 0.76 at 300 and 1000 K, respectively. Our findings reveal that C-BPN has high potency to be used in thermoelectric nano devices with selective anisotropic properties at elevated temperatures. Copyright © 2024, The Authors. All rights reserved.

关键词： Metal insulator transition

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Flash Sintering of Rhenium at Ambient Temperature in < 1 Minute with Electrical Current

SSRN

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SSRN 2023年

作者： Bamidele, Emmanuel A. Weimer, Alan W. Raj, Rishi Materials Science and Engineering Program University of Colorado BoulderCO80309 United States Department of Mechanical Engineering University of Colorado BoulderCO80309-0427 United States Department Chemical and Biological Engineering University of Colorado BoulderCO80309 United States

We show that rhenium can be sintered from powders to nearly full density (99.96%) by the direct injection of dc current (without a furnace) into dogbone shaped specimens in Ar atmosphere ( © 2023, The Authors. Al... 详细信息

关键词： Sintering

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Effects of Incident Angle on Single-Event Leakage Current Degradation in Heavy-Ion Irradiated 1800 v and 4500 v SiC Power MOSFETs

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IEEE Transactions on Nuclear science 2025年

作者： Sengupta, A. Martinella, C. Ball, D.R. Niskanen, K. Senarath, A.S. Islam, S. Harris, P.M. Hutson, J.M. Osheroff, J.M. Sternberg, A.L. Kettunen, H. Kosier, S.L. Grossner, U. Javanainen, A. Galloway, K.F. Schrimpf, R.D. Witulski, A.F. Zürich8092 Switzerland Vanderbilt University Interdisciplinary Materials Science Program NashvilleTN37235 United States Lipscomb University Electrical and Computer Engineering Department NashvilleTN37204 United States NASA/GSFC Code 561.4 GreenbeltMD20771 United States Vanderbilt University Electrical Engineering and Computer Science Department B 351825 NashvilleTN37235 United States University of Jyväskylä Department of Physics Jyväskylä40014 Finland

Experimental heavy-ion responses of two variants of SiC power MOSFETs are evaluated. The devices have similar epitaxial thickness but different doping. The higher doping in the epitaxial region results in lower breakdown voltage, and typically leads to a lower threshold drain voltage at which single-event leakage current (SELC) occurs. Furthermore, the heavy-ion-induced SELC degradation in the drain and gate currents of the SiC MOSFETs exhibit a strong dependence on the heavy-ion's angle of incidence. The devices' behavior significantly alters when irradiated with heavy-ions at different incident angles under the same fixed bias and total fluence, as also confirmed by 3-D Technology Computer Aided Design (TCAD) simulations. © 1963-2012 IEEE.

关键词： Power MOSFET

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Large magnetic anisotropy and magnetostriction in thin films of CoV2O4

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Physical Review materials 2023年第1期7卷 014408-014408页

作者： Sangsoo Kim Christie J. Thompson Yan Xin Christianne Beekman National High Magnetic Field Laboratory Florida State University Tallahassee Florida 32310 USA Department of Physics Florida State University Tallahassee Florida 32306 USA Materials Science and Engineering Program Florida State University Tallahassee Florida 32310 USA

Spinel cobalt vanadate CoV2O4 has been grown on (001) SrTiO3 substrates. Using torque magnetometry experiments, we find that the previously observed temperature-induced anisotropy change, where the easy axis changes from the out-of-plane [001] direction to a biaxial anisotropy with planar <100> easy axes, occurs in a gradual second-order structural phase transition. This paper characterizes this transition and the magnetic anisotropies in the (001), (100), and (1¯10) rotation planes, and explores their field dependence up to 30 T. Below 80 K, hysteretic features appear around the hard axes, i.e., the out-of-plane direction in (1¯10) and (010) rotations and the planar <110> directions in (001) rotations. This is due to a Zeeman energy that originates from the lag of the magnetization with respect to the applied magnetic field as the sample is rotated. The appearance of the hysteresis, which persists up to very high fields, shows that the anisotropy at low temperature is rather strong. Additionally, field-dependent distortions to the symmetry of the torque response in increasing applied fields shows that magnetostriction plays a large role in determining the direction and magnitude of the anisotropy.

关键词： Magnetic anisotropy Magnetic phase transitions Structural properties

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