School of Physics and Telecommunication Engineering, Shaanxi Key Laboratory of Catalysis, Shaanxi University of Technology , Hanzhong 723001, P. R. China.
State Key Laboratory of Mesoscopic Physics and Department of Physics, Peking University , Beijing 100871, P. R. China.
ACS Appl Mater Interfaces. 2017 Jul 12;9(27):23128-23140. doi: 10.1021/acsami.7b03833. Epub 2017 Jun 26.
Bismuthene, a bismuth analogue of graphene, has a moderate band gap, has a high carrier mobility, has a topological nontriviality, has a high stability at room temperature, has an easy transferability, and is very attractive for electronics, optronics, and spintronics. The electrical contact plays a critical role in an actual device. The interfacial properties of monolayer (ML) bismuthene in contact with the metal electrodes spanning a wide work function range in a field-effect transistor configuration are systematically studied for the first time by using both first-principles electronic structure calculations and quantum transport simulations. The ML bismuthene always undergoes metallization upon contact with the six metal electrodes owing to a strong interaction. According to the quantum transport simulations, apparent metal-induced gap states (MIGSs) formed in the semiconductor-metal interface give rise to a strong Fermi-level pinning. As a result, the ML bismuthene forms an n-type Schottky contact with Ir/Ag/Ti electrodes with electron Schottky barrier heights (SBHs) of 0.17, 0.22, and 0.25 eV, respectively, and a p-type Schottky contact with Pt/Al/Au electrodes with hole SBHs of 0.09, 0.16, and 0.38 eV, respectively. The effective channel length of the ML bismuthene transistors is also significantly reduced by the MIGSs. However, the MIGSs are eliminated and the effective channel length is increased when ML graphene is used as an electrode, accompanied by a small hole SBH of 0.06 eV (quasi-Ohmic contact). Hence, an insight is provided into the interfacial properties of the ML bismuthene-metal composite systems and a guidance is provided for the choice of metal electrodes in ML bismuthene devices.
二碲化铋，一种类似石墨烯的铋材料，具有适中的带隙、高载流子迁移率、拓扑非平庸性、室温下的高稳定性、易于转移等特点，在电子学、光电子学和自旋电子学领域具有很大的吸引力。在实际器件中，电接触起着至关重要的作用。本文首次通过第一性原理电子结构计算和量子输运模拟，系统研究了跨越宽功函数范围的金属电极与场效应晶体管配置中单层（ML）二碲化铋的界面性质。由于强烈的相互作用，ML 二碲化铋与六种金属电极接触时总是会发生金属化。根据量子输运模拟，半导体-金属界面处形成的明显金属诱导能隙态（MIGS）导致强费米能级钉扎。因此，ML 二碲化铋与 Ir/Ag/Ti 电极形成 n 型肖特基接触，电子肖特基势垒高度（SBH）分别为 0.17、0.22 和 0.25 eV，与 Pt/Al/Au 电极形成 p 型肖特基接触，空穴 SBH 分别为 0.09、0.16 和 0.38 eV。MIGS 还显著减小了 ML 二碲化铋晶体管的有效沟道长度。然而，当使用 ML 石墨烯作为电极时，MIGS 被消除，有效沟道长度增加，同时空穴 SBH 减小到 0.06 eV（准欧姆接触）。因此，本文深入了解了 ML 二碲化铋-金属复合体系的界面性质，并为 ML 二碲化铋器件中金属电极的选择提供了指导。
