Zeng Jincheng, Liu Gang, Han Yu, Luo Wenwei, Wu Musheng, Xu Bo, Ouyang Chuying
College of Physics and Communication Electronics, Laboratory of Computational Material Physics, Jiangxi Normal University, Nanchang 330022, China.
ACS Omega. 2021 May 25;6(22):14639-14647. doi: 10.1021/acsomega.1c01747. eCollection 2021 Jun 8.
Recently, synthesized Janus MoSSe monolayers have attracted tremendous attention in science and technology due to their novel properties and promising applications. In this work, we investigate their molecular adsorption-induced structural and electronic properties and tunable doping effects under biaxial strain and external electric field by first-principles calculations. We find an effective n-type or p-type doping in the MoSSe monolayer caused by noncovalent tetrathiafulvalene (TTF) or tetracyanoquinodimethane (TCNQ) molecular adsorption. Moreover, the concentration of doping carrier with respect to the S or Se side also exhibits Janus characteristics because of the electronegativity difference between S and Se atoms and the intrinsic dipole moment in the MoSSe monolayer. In particular, this n-type or p-type molecular doping effect can be flexibly tuned by biaxial strain or under external electric field. By analyzing the valence band maximum (VBM) and conduction band minimum (CBM) in the band structure of MoSSe/TTF under strain, the strain-tunable band gap of MoSSe and the n-type molecular doping effect is revealed. Further explanation of charge transfer between TTF or TCNQ and the MoSSe monolayer by an equivalent capacitor model shows that the superimposition of external electric field and molecular adsorption-induced internal electric field plays a crucial role in achieving a controllable doping concentration in the MoSSe monolayer.
近年来，合成的Janus MoSSe单层因其新颖的性质和广阔的应用前景而在科学技术领域引起了极大关注。在这项工作中，我们通过第一性原理计算研究了它们在双轴应变和外部电场下分子吸附诱导的结构和电子性质以及可调谐的掺杂效应。我们发现，非共价四硫富瓦烯（TTF）或四氰基对苯二醌二甲烷（TCNQ）分子吸附会在MoSSe单层中导致有效的n型或p型掺杂。此外，由于S和Se原子之间的电负性差异以及MoSSe单层中的固有偶极矩，相对于S或Se侧的掺杂载流子浓度也呈现出Janus特性。特别地，这种n型或p型分子掺杂效应可以通过双轴应变或在外部电场下灵活调节。通过分析应变下MoSSe/TTF能带结构中的价带最大值（VBM）和导带最小值（CBM），揭示了MoSSe的应变可调带隙和n型分子掺杂效应。通过等效电容模型对TTF或TCNQ与MoSSe单层之间电荷转移的进一步解释表明，外部电场和分子吸附诱导的内电场的叠加在实现MoSSe单层中可控的掺杂浓度方面起着关键作用。
