Xu Linqiang, Liu Shiqi, Zhang Han, Zhang Xiuying, Li Jingzhen, Yan Jiahuan, Shi Bowen, Yang Jie, Yang Chen, Xu Lianqiang, Sun Xiaotian, Lu Jing
State Key Laboratory of Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, P. R. China.
School of Physics and Electronic Information Engineering, Engineering Research Center of Nanostructure and Functional Materials, Ningxia Normal University, Guyuan, Ningxia 756000, P. R. China.
Phys Chem Chem Phys. 2020 Apr 15;22(15):7853-7863. doi: 10.1039/d0cp00058b.
Monolayer (ML) MoS2 is one of the most extensively studied two-dimensional (2D) semiconductors. However, it suffers from low carrier mobility and pervasive Schottky contact with metal electrodes. 2D semiconductor Bi2O2S, a sulfur analogue of 2D Bi2O2Se, has been prepared recently. ML fully hydrogen-passivated Bi2O2S2 (Bi2O2S2H2) posseses a comparable band gap (1.92 eV) with ML MoS2 (1.8 eV), but probably has a better device performance than ML MoS2. Based on the density functional theory, the electron and hole mobilities of ML Bi2O2S2H2 at 300 K are calculated to be 16 447-26 699 and 264-968 cm2 V-1 s-1, respectively. Then we firstly characterize the contact properties of ML half hydrogen-passivated Bi2O2S2 (Bi2O2S2H) with four bulk metal electrodes (Ti, Sc, Pd, and Pt) based on ab initio quantum transport simulation. In the lateral direction, a p-type Schottky contact is found in Pd and Pt electrodes, and the corresponding hole Schottky barrier heights (SBHs) are 0.54 and 0.99 eV, respectively. Remarkably, a coveted n-type Ohmic contact appears in Sc and Ti electrodes. Finally, the current on-off ratio of the ML hydrogen-passivated Bi2O2S2 field effect transistor with a Ti electrode reaches 105. Hence, the good intrinsic properties, contact properties, and large switching ability put ML hydrogen-passivated Bi2O2S2 in the rank of potential channel candidates for post-silicon era field effect transistors.
单层（ML）二硫化钼是研究最为广泛的二维（2D）半导体之一。然而，它存在载流子迁移率低以及与金属电极普遍存在肖特基接触的问题。二维半导体Bi2O2S，作为二维Bi2O2Se的硫类似物，最近已被制备出来。完全氢钝化的单层Bi2O2S2（Bi2O2S2H2）具有与单层二硫化钼（1.8 eV）相当的带隙（1.92 eV），但可能具有比单层二硫化钼更好的器件性能。基于密度泛函理论，计算出单层Bi2O2S2H2在300 K时的电子和空穴迁移率分别为16447 - 26699和264 - 968 cm2 V-1 s-1。然后，我们基于从头算量子输运模拟，首次表征了单层半氢钝化Bi2O2S2（Bi2O2S2H）与四种体金属电极（Ti、Sc、Pd和Pt）的接触特性。在横向方向上，在Pd和Pt电极中发现了p型肖特基接触，相应的空穴肖特基势垒高度（SBHs）分别为0.54和0.99 eV。值得注意的是，在Sc和Ti电极中出现了令人向往的n型欧姆接触。最后，具有Ti电极的单层氢钝化Bi2O2S2场效应晶体管的电流开/关比达到105。因此，良好的本征特性、接触特性和大开关能力使单层氢钝化Bi2O2S2跻身于硅后时代场效应晶体管潜在沟道候选材料之列。
