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361 results on '"Li, Xian-Bin"'

4. Inert gas as electronic impurity in semiconductors: The case for active infrared absorption in silicon

Author

Chen, Nian-Ke, Gao, Yu-Chen, Zhao, Ji-Hong, Li, Chun-Hao, Chen, Qi-Dai, Sun, Hong-Bo, Zhang, Shengbai, and Li, Xian-Bin

Subjects
Condensed Matter - Materials Science
Abstract

Inert (noble gas) elements are extremely inactive to surrounding chemical environment and are frequently employed as protective gas in various semiconductor fabrication processes. In this work, we surprisingly discover that high doses of argon up to $10^{17}-10^{20} cm^{-3}$ can be measured in silicon exposed by laser pulses even after 1300 days. First-principles calculations and molecular dynamics identify a unique argon-locking-vacancy (ALV) defect atomic model in silicon. The ALV defect is dynamically robust in contrast to the frequently moving pure Si vacancy. While argon is chemically inert, it readily modulates defect states of the occupied vacancy via steric repulsion and rattling motions, leading to significant band splitting within bandgap and thus strong infrared absorptions. Moreover, the repulsion between substitutional argon and dangling bonds results in shallow donors which explains the confusion of enhanced n-type carriers in experiments. The work paves a way of using noble gas element to produce active infrared absorption source for the non-heteroepitaxy photonic detectors directly on silicon wafer at infrared communication wavelength.

Published
2023
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12. Intensive Structural Disorder Induces Electronic Delocalization: Amorphous Solid‐Liquid Transition in Ovonic Threshold Switching Materials.

Author

Chen, Nian‐Ke, Wang, Bai‐Qian, Niu, Meng, Sun, Hong‐Bo, Zhang, Shengbai, and Li, Xian‐Bin

Subjects
CARRIER density, BAND gaps, ELECTRONIC structure, OPEN-ended questions, MELTING
Abstract

Disorder‐induced electronic localization is responsible for the OFF state of the Ovonic threshold switching (OTS) device, which is an indispensable component in the present 3D‐crossbar‐architecture phase‐change memory circuit. However, the atomic mechanism of the OTS device, especially the role of thermal effect, remains a long‐term open question. Recent researches suggest that the working current of the OTS ON‐state is often large enough to melt the adjacent phase‐change memory material in the OTS+PCM devices. Thus, Joule heating‐induced atomic/electronic structure transition in OTS materials must be seriously considered. Taking the typical OTS material GeSe as an example, first‐principles calculations reveal an unexpected electronic delocalization induced by the enhanced structural disorder upon solid‐liquid transition. Meanwhile, as the temperature rises, the band gap decreases or even closes, leading to an increase in carrier concentration. Therefore, the melting filament with high conductivity could be responsible for the holding‐ON state of OTS materials. The results in this study may provide possible explanations for some puzzles of OTS devices, such as the reasons for holding‐ON state and limited endurance. [ABSTRACT FROM AUTHOR]

Published
2024
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16. Atomic and electronic origin of robust off-state insulation properties in Al-rich AlxTey glass for ovonic threshold switching applications.

Author

Li, Xiao-Dong, Tian, Maoan, Wang, Bai-Qian, Chen, Nian-Ke, and Li, Xian-Bin

Subjects
COORDINATE covalent bond, GLASS, COVALENT bonds, METAL bonding, BOND index funds, METALLIC glasses
Abstract

Ovonic threshold switching (OTS) selectors play a critical role in suppressing the sneak-path current of three-dimensional crossbar integration circuits. Compared to conventional nonmetal-telluride OTS selectors, selectors based on AlxTey glass are found to have both satisfactory on-state current and selectivity. However, it is unclear why the Al-rich AlxTey glass-based OTS selectors have robust insulation properties for reducing the off-state current. This work reveals the structure–property correlations of amorphous AlxTey at the atomic scale by first-principles calculations. It is found that the stoichiometric Al2Te3 glass tends to have a clean bandgap owing to the covalent and dative bonds formed by non-equivalent sp3-hybridized Al orbitals and the lone-pair electrons of Te. Unexpectedly, for Al-rich AlxTey glass (Al2.21Te2.79), the Al–Al bonds formed by redundant Al-atoms have an integrated crystal orbital bond index (ICOBI) of 0.8–0.9, which is much larger than that of Al–Al bonds in pure metals (0.227), indicating they are covalent. It is the covalent Al–Al bonds that ensure the robust insulation characteristics of Al-rich AlxTey glass, while the Te–Te interaction in the Al-poor AlxTey glass (Al1.79Te3.21) produces midgap states, thereby reducing the insulativity. The presented atomic and electronic pictures here will provide useful theoretical insights for designing OTS selectors with improved performances. [ABSTRACT FROM AUTHOR]

Published
2023
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17. Complex charge density waves in simple electronic systems of two-dimensional III2–VI3 materials.

Author

Huang, Yu-Ting, Li, Zhen-Ze, Chen, Nian-Ke, Wang, Yeliang, Sun, Hong-Bo, Zhang, Shengbai, and Li, Xian-Bin

Subjects
CHARGE density waves, ELECTRON-phonon interactions, FERMI surfaces, BRILLOUIN zones, ELECTRON density
Abstract

Charge density wave (CDW) is the phenomenon of a material that undergoes a spontaneous lattice distortion and modulation of the electron density. Typically, the formation of CDW is attributed to Fermi surface nesting or electron-phonon coupling, where the CDW vector (QCDW) corresponds to localized extreme points of electronic susceptibility or imaginary phonon frequencies. Here, we propose a new family of multiple CDW orders, including chiral Star-of-David configuration in nine 2D III2–VI3 van der Waals materials, backed by first-principles calculations. The distinct feature of this system is the presence of large and flat imaginary frequencies in the optical phonon branch across the Brillouin zone, which facilitates the formation of the diverse CDW phases. The electronic structures of 2D III2–VI3 materials are relatively simple, with only III-s,p and VI-p orbitals contributing to the formation of the CDW order. Despite that, the CDW transitions involve both metal-to-insulator and insulator-to-insulator transitions, accompanied by a significant increase in the bandgap caused by an enhanced electronic localization. Our study not only reveals a new dimension in the family of 2D CDWs, but is also expected to offer deeper insights into the origins of the CDWs. This study introduces a family of multiple charge-density-wave orders in 2D III2–VI3 materials, including the chiral Star-of-David configuration. The charge-density-wave transitions involve both metal-to-insulator and insulator-to-insulator transitions, providing a platform for understanding the origins of charge density waves. [ABSTRACT FROM AUTHOR]

Published
2024
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