新型二维原子合金Mo1-xWxSe2的结构和能带及其关联关系研究

The new two-dimensional material with the sizable and tunable bandgap is necessary for their application in nanoelectronics and optoelectronics. However, at present the available two-dimensional materials are limited.Many efforts have been made to tune the band gaps of two-dimensional materials,but the process is unsatisfactory. Here we propose a new approach,i.e. apploying, to tune the band gaps of two dimensional materials. We have investigated the two-dimensional transition metal dichalcogenide Mo1-xWxS2 monolayers. The preliminary experimental results (manuscript under review)indicated that tunable band gaps have been achieved in two dimensional Mo1-xWxS2 monolayers with band gap from 1.82 eV(at x=0.2) to 1.99 eV(at x=1). Alloying can be a promissing way to the band gap tuning and application of two-dimensional materials. In this work, we will expand two-dimensional alloy materials.The photoluminescence and Raman spectra of two dimensional alloy Mo1-xWxSe2 will be investigated. We hope that alloying can provide new opportunity to the application of new two-dimensional materials. Meanwhile, the variation of electronic structure and microscopic crystal structure of two-dimensional Mo1-xWxSe2 alloy with composition, layer number, temperature and strain will be studied systematically. The origin of the variation will be analyzed, so that the fundamental physical properties of two dimensional alloy Mo1-xWxSe2 can be further understood.

基于二维材料的纳米电子学、光电子学的发展迫切需要具有合适且连续可调带隙的新二维材料。本课题组率先开展的二维过渡金属二硫族化物Mo1-xWxS2合金的相关研究表明：通过调节Mo/W的组分，可以实现对二维合金Mo1-xWxS2带隙的连续调控。本项目拟进一步拓展二维合金材料体系，以显微荧光/拉曼光谱技术为手段，通过研究二维原子合金Mo1-xWxSe2荧光光谱随不同组分、层数、温度和应力的变化，揭示带隙的变化规律；通过研究其拉曼光谱峰位、峰宽等在上述不同条件下的变化，系统研究其微观晶体结构的变化，并揭示这些变化的物理根源；通过比较荧光光谱和拉曼光谱的变化规律，揭示二维原子合金Mo1-xWxSe2能带和晶体结构（对称性、原子排布、原子间距、形变等）的内在关联。本项目的开展有助于加深对新二维合金材料Mo1-xWxSe2基本物理性能的理解和认识，同时为二维材料能带调控提供研究思路，为其实际应用打下基础。

基于二维材料的纳米电子学、光电子学的发展迫切需要具有合适且连续可调带隙的新型二维材料。本项目在前期开展的二维过渡金属二硫族化物Mo1-xWxS2合金的相关研究的基础上，进一步拓展了二维合金材料体系，开展了“新型二维原子合金Mo1-xWxSe2的结构和能带及其关联关系研究”，取得了一些重要结果，主要包括（1）以显微荧光/拉曼光谱技术为手段，研究了二维原子合金Mo1-xWxSe2荧光和拉曼光谱随不同组分、层数的变化，结果表明：二维原子合金Mo1-xWxSe2单层是直接带隙半导体，而其块体是间接带隙半导体；二维原子合金Mo1-xWxSe2的带隙随组分、层数可调；单层Mo1-xWxSe2合金的带隙从1.56 eV到1.65 eV,且带隙变化呈“能带弯曲“效应；单层Mo1-xWxSe2合金的偏振拉曼光谱研究表明其面外振动一级模A1g呈“单模”行为,而其面内振动E2g模和所有的二级拉曼模呈“双模”行为。不同层数（1-3层和块体）Mo1-xWxSe2合金的荧光/拉曼光谱研究表明，其荧光和拉曼峰差随层数呈规律变化，因此显微荧光/拉曼光谱技术可以作为判定合金层数的简单工具。（2）单层Mo1-xWxSe2合金的电学性质测量结果表明Mo1-xWxSe2合金是n型半导体，且具有高开关比(10(5))。本项目的开展为二维材料能带调控提供了新的研究思路和方法。