Article
Physics, Multidisciplinary
Kazuo Soda, Daiki Kato, Mai Komabuchi, Toshiki Terabe, Shin Takayama, Toshiki Ibaragi, Masahiko Kato, Ken Niwa, Masashi Hasegawa, Shoichi Takakura, Masashi Nakatake
Summary: The electronic structure of newly synthesized marcasite-type cobalt pernitride (CoN2) was investigated using XAS and XPS, and the physical properties were discussed in terms of the obtained electronic structures. In contrast to pyrite-type pernitrides, marcasite-type cobalt pernitride exhibits ferromagnetic metal properties.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2021)
Article
Nanoscience & Nanotechnology
Yongcheng Liang, Xiao-Feng Wei, Chao Gu, Ji-Xuan Liu, Fei Li, Mingqi Yan, Xingwei Zheng, Zhilin Han, Yusheng Zhao, Shanmin Wang, Jiong Yang, Wenqing Zhang, Liangzhi Kou, Guo-Jun Zhang
Summary: An efficient strategy for enhancing the hardness of transition-metal monocarbides (TMCs) by optimally filling the bonding orbitals of valence electrons has been reported. Newly developed W1-xRexC samples show significantly enhanced hardness compared to their parent phase (WC), making them the hardest TMCs for practical applications. The hardness enhancement can be rationalized by the balanced occupancy of bonding and antibonding states, offering a guide for the design of other hard and superhard compounds.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Chemistry, Physical
Jinjia Liu, Tao Yang, Qing Peng, Yong Yang, Yong-Wang Li, Xiao-Dong Wen
Summary: Investigating the interaction between hydrogen and four typical surfaces of pyrite FeS2 through density functional theory calculations revealed that hydrogen dissociative adsorption on the (210) surface is favorable. However, it is unfavorable on the (100) and (211) surfaces due to high activation barriers. Pure molecule adsorption mode is favorable on the (100) facet for high adsorption coverage.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Multidisciplinary
Majed S. Fataftah, Brandon Q. Mercado, Patrick L. Holland
Summary: This article reports two mixed-valent diiron complexes with carbon bridges, and demonstrates the ability of carbon bridges to stabilize the valence delocalized ground states in mixed-valent iron dimers through experimental and computational studies.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
S. R. Kandel, B. B. Dumre, D. Gall, S. V. Khare
Summary: We have studied the properties of 29 transition metal nitrides using density functional theory calculations. Only 5 compounds were found to be both vibrationally and mechanically stable, with CrN6 having the highest Vickers hardness. The hardness is directly proportional to mass density and inversely proportional to M-M and M-N bond lengths. The band structure analysis showed that all stable compounds except HgN6 are metallic in nature. Magnetic properties were found in only 8 compounds.
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
(2022)
Article
Chemistry, Inorganic & Nuclear
Yu-Qi Chen, Huan-Huan Zhang, Bo Wen, Xi-Bo Li, Xiao-Lin Wei, Wen-Jin Yin, Li-Min Liu, Gilberto Teobaldi
Summary: This study extensively investigates the electronic properties and Schottky barrier height (E-SBH) of several vdW Janus MXY/graphene heterostructures through first-principles simulations. The results reveal that by modifying the composition and geometry of the heterostructure's interface, the electrical contact can be controlled, with a potential variation of up to a factor of seven in the E-SBH.
DALTON TRANSACTIONS
(2022)
Article
Materials Science, Multidisciplinary
Barbara Schmid, Nikola Koutna, Rainer Hahn, Tomasz Wojcik, Peter Polcik, Paul Heinz Mayrhofer
Summary: Transition metal carbides are high-temperature ceramics with high thermal and mechanical stability and melting points above 4000 degrees C. However, their high brittleness is a significant limitation. Inspired by nanolayered superlattice architecture, TaC/HfC and TiC/TaC superlattice films were developed to enhance hardness and toughness. The superlattice structure of TiC/TaC was pronounced, while TaC/HfC showed more of a solid solution characteristic. The TiC/TaC superlattices have higher hardness and better fracture behavior than TaC/HfC coatings, as well as monolithic TiC, TaC, and HfC coatings.
INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
I Castillo, T. Sohier, M. Paillet, D. Cakiroglu, C. Consejo, C. Wen, F. Wasem Klein, M-Q Zhao, A. Ouerghi, S. Contreras, A. T. Charlie Johnson, M. J. Verstraete, B. Jouault, S. Nanot
Summary: We performed transport measurements in monolayer MoS2 devices close to the bottom of the conduction band edge. The measured effective mobility is one of the highest among CVD-grown MoS2 monolayer devices. The electronic transport in the insulating regime is dominated by thermally activated transport at high temperature and Efros-Schklovkii variable range hopping at lower temperatures.
Article
Chemistry, Multidisciplinary
Guiqian Sun, Xingbin Zhao, Lu Chen, Yubo Fu, Wei Zhao, Meiyan Ye, Fei Wang, Qiang Tao, Shushan Dong, Pinwen Zhu
Summary: Nickel borides are promising materials with high hardness and excellent properties in catalysis and magnetism. The crystallization of Ni-B compounds with micro-size is still a challenge, and this study successfully synthesized single phases of various Ni-B compounds using high pressure and high temperature. The growth process of Ni-B compounds was found to involve Ni covering B to form Ni-B compounds. The findings of this work are significant for guiding the synthesis of highly crystalline transition metal borides in the future.
Article
Materials Science, Multidisciplinary
S. R. Kandel, B. B. Dumre, D. Gall, S. V. Khare
Summary: We investigated the properties of 29 nitrogen-rich transition metal nitrides using density functional theory-based calculations. Only 13 of these compounds were found to be mechanically and vibrationally stable, with FeN6 predicted to be the hardest compound. Compounds from group 8 elements (FeN6, RuN6, and OsN6) were predicted to be the hardest and have the highest densities, with hardness primarily attributed to M-N and M-M interactions. Eight of the compounds also exhibited a magnetic moment.
COMPUTATIONAL MATERIALS SCIENCE
(2023)
Review
Chemistry, Physical
Songyu Li, Yang Ma, Nabonswende Aida Nadege Ouedraogo, Famin Liu, Congya You, Wenjie Deng, Yongzhe Zhang
Summary: This review summarizes various strategies for p-/n-type modulation of TMDCs, including controlling intrinsic defects, doping, surface charge transfer, chemical intercalation, electrostatic modulation, and dielectric interface engineering. The mechanisms and comparisons of these strategies are analyzed, along with a discussion of their device applications in electronics and optoelectronics. Challenges and outlooks for p-/n-type modulation of TMDCs are presented for future research references.
Article
Materials Science, Multidisciplinary
N. Siminel, K. Sushkevich, S. Aazou, A. Micu, A. Siminel, Z. Sekkat, L. Kulyuk
Summary: The temperature dependence of the luminescence spectra of MoSe2 crystals intercalated with I2 molecules has been investigated. The luminescence spectrum consists of a zero-phonon doublet and its phonon replicas, caused by the recombination of excitons bound on iodine molecules embedded in the van der Waals gap. The rate of radiative recombination of the B state is found to be 76 times higher than the A state.
OPTICAL MATERIALS EXPRESS
(2023)
Article
Engineering, Environmental
Yujun Xu, Cuicui Du, Qinghui Shen, Junlin Huang, Xiaohua Zhang, Jinhua Chen
Summary: The study synthesized well-dispersed RuS2 nanoparticles as an excellent electrocatalyst for alkaline hydrogen evolution reaction. By anchoring these nanoparticles on nitrogen and sulfur co-doped porous carbon spheres, the active sites were increased, electronic structure was modified, and catalytic activity was enhanced.
CHEMICAL ENGINEERING JOURNAL
(2021)
Article
Chemistry, Multidisciplinary
Shubham Tyagi, Paresh C. Rout, Ulrike Luders, Ulrich Eckern, Udo Schwingenschlogl
Summary: The electronic and magnetic properties of (LaCrO3)(m)/SrCrO3 superlattices are investigated using first principles calculations. It is found that the magnetization in the superlattices is dependent on the value of m, due to charge ordering with different oxidation states of Cr ions. The transparent p-type semiconductors with finite magnetization can be used to fabricate transparent magnetic diodes and transistors with potential technological applications.
NANOSCALE ADVANCES
(2023)
Article
Chemistry, Physical
Xueying Guo, Tilong Yang, Fu Kit Sheong, Zhenyang Lin
Summary: This study systematically investigates the reactivity of metal-boryl complexes using density functional theory calculations, revealing that the nucleophilic feature of boryl is diminished when the metal is more electronegative. The empty p orbital of boron and the d electrons in the metal can also influence the reactivity of the complex.
Article
Materials Science, Coatings & Films
Peijiao Fang, Baiwei Wang, Daniel Gall
Summary: Molybdenum carbide thin films were deposited on Al2O3 substrates using reactive DC magnetron sputtering, revealing that an optimal CH4 fraction of 7-8% leads to epitaxial delta-MoCy and biaxial textured beta-Mo2C, while lower or higher CH4 fractions yield polycrystalline or nanocrystalline structures.
SURFACE & COATINGS TECHNOLOGY
(2021)
Article
Physics, Applied
Atharv Jog, Erik Milosevic, Pengyuan Zheng, Daniel Gall
Summary: In situ transport measurements show that adatoms on Cu and Co surfaces significantly disturb the surface potential, leading to electron scattering and resistance increase, while this effect is negligible for Rh. The measured inverse correlation between electronegativity and resistance change suggests that the surface potential perturbation is the primary parameter affecting electron surface scattering in thin metal layers. Electronegative metals, in particular, are promising conductors for highly scaled interconnect lines.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Physical
I. Khatri, N. J. Szymanski, B. B. Dumre, J. G. Amar, D. Gall, S. V. Khare
Summary: The study investigated the electronic structures, formation energies, and phonon dispersion curves of transition metal carbides using first principles calculations, proposing a theoretical framework for controlling their stability. Mechanical properties were explored through calculation of elastic tensors and observable properties such as hardness and ductility, demonstrating the correlation between robust mechanical performance and complete filling of bonding orbitals.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Materials Science, Multidisciplinary
Peijiao Fang, C. P. Mulligan, Ru Jia, Jian Shi, S. Khare, Daniel Gall
Summary: In this study, titanium carbide films were deposited onto MgO(001) substrates using reactive magnetron sputtering. The microstructure of the films was dominated by a TiCx(001) matrix, and the presence of secondary phases affected the hardness and elastic modulus. The solubility of carbon in the cubic phase was predicted to be low.
Article
Physics, Applied
Tianji Zhou, Atharv Jog, Daniel Gall
Summary: The electron reflection probability at symmetric twin boundaries in eight face-centered cubic (fcc) metals was predicted from first principles. The results showed that the reflection probability increases as the interplanar distance decreases. An extrapolation scheme was proposed to estimate the reflection probability at random grain boundaries. It was found that Cu, Ag, and Au have relatively small reflection probabilities due to their nearly spherical Fermi surfaces, while Al, Ca, Ni, Rh, and Ir have approximately two times higher probabilities. The resistivity of metals with randomly oriented grains was found to be proportional to the bulk resistivity, electron mean free path, and reflection probability. Cu had the lowest resistivity, suggesting that other fcc metals have higher resistivity in the limit of small randomly oriented grains. Therefore, the conductivity benefit of replacement metals for narrow Cu interconnect lines can only be achieved if the grains are larger than the linewidth or exhibit symmetric orientation relationships.
APPLIED PHYSICS LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Atharv Jog, Daniel Gall
Summary: The resistivity size effect in Rh has been investigated by studying electron scattering at surfaces and grain boundaries. The results show that Rh has better conductivity than Cu for narrow interconnect lines, and achieving large grain size is essential for realizing the conductivity advantage.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Electrochemistry
Prachi Pragnya, Daniel Gall, Robert Hull
Summary: In situ transmission electron microscopy (TEM) techniques were used to study the corrosion of Inconel-625 alloy under different conditions. The results showed that the corrosion rate increased significantly at high temperatures and in the presence of oxygen. Salt hydration also accelerated the corrosion process. The researchers suggested that adjusting the composition of chloride melts could reduce the corrosion rate.
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
(2022)
Article
Chemistry, Multidisciplinary
Christopher Perez, Atharv Jog, Heungdong Kwon, Daniel Gall, Mehdi Asheghi, Suhas Kumar, Woosung Park, Kenneth E. Goodson
Summary: In this study, time-domain thermoreflectance was used to uncover cross-plane heat conduction mechanisms in high aspect ratio metal nanostructures. The findings demonstrate the existence of unexplored heat transport modes in nanostructured metals, which can be utilized to develop electro-thermal solutions for modern microelectronic devices and sensors.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Engineering, Electrical & Electronic
Minghua Zhang, Daniel Gall
Summary: Epitaxial CuAl2 layers with different thicknesses were deposited on MgO substrates by co-sputtering and their resistivity was measured. The results show that the resistivity of CuAl2 increases with decreasing thickness, with electron scattering at Al vacancies playing a significant role. The Fuchs-Sondheimer model was used to describe the resistivity scaling and the electron mean free path at room temperature. Transport measurements at 77K indicate a more pronounced resistivity size effect in CuAl2.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Materials Science, Multidisciplinary
Sushant Kumar, Christian Multunas, Benjamin Defay, Daniel Gall, Ravishankar Sundararaman
Summary: Increasing resistivity of metal wires with reducing nanoscale dimensions is a major performance bottleneck of semiconductor computing technologies. Metals with anisotropic Fermi velocity distributions can effectively suppress electron scattering by surfaces and outperform isotropic conductors. Certain intermetallics and borides with anisotropic Fermi velocities show the most promising performance for narrow wires.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
S. R. Kandel, B. B. Dumre, D. Gall, S. Khare
Summary: It has been discovered that hexa-nitrides have higher hardness than conventional nitrides in transition metal nitrides. Only eight transition metal nitrides are stable in both mechanics and dynamics. Among them, h-WN6 has a higher hardness, while h-ZnN6 has a lower hardness, determined by crystal structure and composition.
Article
Physics, Applied
Minghua Zhang, Sushant Kumar, Ravishankar Sundararaman, Daniel Gall
Summary: The resistivity size effect in the ordered intermetallic CuTi compound was quantified using in situ and ex situ thin film resistivity measurements, as well as density functional theory calculations. The results showed that the measured resistivity and electron mean free path were in agreement with theoretical calculations, but the measured resistivity mean free path product was almost 2.4 times larger than predicted, indicating a breakdown of classical transport models.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Atharv Jog, Pengyuan Zheng, Tianji Zhou, Daniel Gall
Summary: In this study, Mo(001) and Mo(011) layers were sputter-deposited onto MgO(001) and alpha-Al2O3(11 (2) over bar0) substrates with thicknesses ranging from 4 to 400 nm. The resistivity of these layers was measured in situ and ex situ at room temperature and 77 K to investigate the resistivity size effect. Both Mo(001) and Mo(011) layers showed an increase in resistivity as the thickness decreased, which was attributed to electron surface scattering. The measurements and simulations confirmed the anisotropy in resistivity size effect, with the Mo(011) orientation exhibiting a smaller effect compared to Mo(001). The overall results indicated that Mo has a relatively small resistivity size effect, making it a promising conductor for narrow interconnects.
Article
Physics, Applied
Minghua Zhang, Daniel Gall
Summary: The epitaxial VNi2 layers deposited on MgO(001) exhibit a resistivity size effect, with a minimum resistivity observed at stoichiometric composition and specific growth temperature. The atomic disorder at domain boundaries in the layers affects the resistivity, and the thickness has a limited impact on the resistivity. The theoretically predicted superior directional conduction in VNi2 cannot be confirmed experimentally in this study. This research provides guidance for the application of VNi2 compound.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
Zonghuan Lu, Lihua Zhang, Xixing Wen, Atharv Jog, Kim Kisslinger, Lei Gao, Jian Shi, Daniel Gall, Morris A. Washington, Gwo-Ching Wang, Toh-Ming Lu
Summary: In this study, a quasi van der Waals epitaxy approach was used to prepare an epitaxial Ru ultrathin film on large-scale, single-crystalline, monolayer graphene. The Ru films on graphene demonstrated significantly reduced electrical resistivity compared to their counterparts grown on bare SiO2.
ACS APPLIED ELECTRONIC MATERIALS
(2022)
