金属-Bi_(2)OS_(2)界面肖特基势垒以及电荷转移机制研究  

Schottky barrier heights and mechanism of charge transfer at metal-Bi_(2)OS_(2) interfaces

作　　者：张晓东 冯丽萍 钟诗宸 叶元茗 潘海曦 刘鹏飞 郑孝奇 李焕勇 屈铭洋 王锡桐 Xiaodong Zhang;Liping Feng;Shichen Zhong;Yuanming Ye;Haixi Pan;Pengfei Liu;Xiaoqi Zheng;Huanyong Li;Mingyang Qu;Xitong Wang(State Key Lab of Solidification Processing,College of Materials Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China)

机构地区：[1]State Key Lab of Solidification Processing,College of Materials Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China

出　　处：《Science China Materials》2023年第2期811-818,共8页中国科学（材料科学（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(62074130);the Natural Science Basic Research Plan in Shaanxi Province of China(2021JM-057);the Research Fund of the State Key Laboratory of Solidification Processing(Northwestern Polytechnical University(NPU),2021-TS-09);the Testing Fund Project of Analysis and Testing Center(NPU)(2021T017)。

摘　　要：由于金属与二维半导体接触界面复杂的电荷转移,界面处经常会产生强烈的费米钉扎效应.本文以Bi_(2)OS_(2)(拥有目前二维半导体材料中已知的最高电子迁移率)作为二维沟道层,采用密度泛函理论系统地计算了其与金属电极接触界面的肖特基势垒以及界面电荷转移机制.当Bi_(2)OS_(2)与三维金属电极接触时,界面强的电荷转移主要由化学键的形成以及泡利电荷排斥作用引起,导致界面具有强的费米钉扎,并且由这两个原因引起的电荷转移方向相反.此外,当金属的功函数大于半导体的电离能或小于半导体的电子亲合能时,界面会产生一个额外的电荷转移.当Bi_(2)OS_(2)与二维金属电极接触时,界面的费米钉扎完全被抑制,界面遵循肖特基-莫特定律,这是因为本文所选用的二维金属电极能够有效地屏蔽泡利电荷排斥作用.因此,通过选择不同功函数的二维金属电极,能够宽范围、线性地调节界面的肖特基势垒高度,并且能够实现界面从n型欧姆接触到p型欧姆接触的转变.这项研究不仅为Bi_(2)OS_(2)基器件的电极选择提供了理论指导,还能够增强对金属与二维半导体接触界面相互作用机制的理解.Strong Fermi-level pinning(FLP)always occurs at the two-dimensional(2D)semiconductor-metal interface due to the complex interfacial charge transfer.By using monolayer(ML)Bi_(2)OS_(2),an emerging 2D semiconductor with the highest electron mobility,the Schottky barrier heights(SBHs)and origin of charge transfer at Bi_(2)OS_(2)-metal interfaces are systematically studied based on density functional theory calculations.In 3D metal-Bi_(2)OS_(2) interfaces,the formation of chemical bonding and the effect of Pauli exchange repulsion are found to be responsible for the strong interfacial charge transfer,resulting in strong FLP,and the direction of charge transfer induced by the two factors is opposite.Besides,an extra interfacial charge transfer is expected to equilibrate the Fermi level when the work functions(WFs)of metal electrodes are out of the range of electron affinity energy and ionization energy of semiconductors.For 2D metal-ML Bi_(2)OS_(2) interfaces,surprisingly,the FLP is found to be entirely suppressed,and thereby,the 2D metal-Bi_(2)OS_(2) contacts obey the conventional Schottky-Mott model.Such intriguing behavior arises from the 2D metal electrodes chosen in this work can effectively shield the effect of Pauli exchange repulsion.Consequently,wide-range and linear-tunable SBHs can be obtained and the conversion from n-type Ohmic contact to p-type Ohmic contact can be achieved by using 2D metal electrodes with different WFs.This study not only provides a theoretical foundation for selecting favorable metal electrodes in devices based on ML Bi_(2)OS_(2),but also helps to enhance the understanding of the mechanism of interface interaction between metals and 2D semiconductors.

关 键 词：肖特基势垒 功函数 欧姆接触 金属电极 电荷转移 接触界面 排斥作用 电子亲合能 

分 类 号：TB34[一般工业技术—材料科学与工程]