连续均一相二维MoS2晶体的谷电子输运机制和物理机理研究

2D semiconductor monolayer molybdenum disulfide (MoS2) is a promising post-silicon material for its unique properties such as wide band gap and non-dangling bonds, etc. In this proposal we aim at to grow 2D continuous homogeneous phase MoS2 films by using chemical vapor deposition method, to increase or decrease the interlayer atoms coupling effect in a controlled manner, and to change the inversion symmetry of the material, in-depth understanding its inner mechanism; we also investigate the emergence and disappearance of the electronic states, control the quantum properties of valleys and other physics of the band structures, and explore the film growth and the physical mechanisms for larger size, non- or very little defects materials. By regulating the energy band structure, combined with transistor topology design, we investigate the 2D MoS2 photoluminescence quantum spin Hall effect and the valley effects by using of light-induced effects. Further, we reveal the mechanism of exciton fluorescence properties and the valley polarization in the 2D layered atomic material, in-depth understanding the relations between the life of the valley polarization, the valley electronics/spin lifetime and the temperature, applied field (electric, light field, etc.) and the material structures design (layers, doping, suspension or adsorption on different substrates, and defects as well), and the influence of the physical mechanism. The research on the effect of micro and nano structures of the MoS2 transistor prototype devices on performance will have an impact on further development on MoS2 Valley electronics.

单层二硫化钼材料以宽禁带、无悬挂键等二维半导体特性是一种很有潜力的后硅时代材料，本研究基于化学气相沉积方法生长连续均一相二维MoS2薄膜，控制原子间的层间耦合的增减变化，改变材料的中心反演对称，深入理解其内在机制；探讨电子态的产生和消失，对能带结构、能谷等物理特性进行量子操控，探索较大尺寸、无或极少材料缺陷薄膜生长机制和物理机理；通过调控能带结构，结合晶体管拓扑结构设计，采用光诱导作用， 研究MoS2二维材料中光致量子自旋和谷霍尔效应，进一步探索二维层状原子晶体中激子荧光性质和谷极化度的机理；深入理解谷极化寿命、谷电子/自旋寿命受温度、外场（电场、光场等）和材料设计调控（层数、掺杂、悬浮或者吸附在不同衬底，以及缺陷）的影响规律与物理机制，进一步研究具有微纳结构的MoS2晶体管原型器件对性能的影响，为二维MoS2谷电子学发展具有一定借鉴意义。

采用化学气相沉积方法（CVD）在SiO2/Si衬底上制备出大面积、尺寸均一的二硫化钼纳米薄膜，采用第一性原理的密度泛函理论研究了拉应力对单层MoS2电子能带结构的影响，计算结果表明，应力对单层MoS2的能带结构影响很强，在单层MoS2的a1，a2方向上均匀施加拉应变0.5%时，其能带就由直接带隙变为间接带隙，并且其禁带宽度随着应力的增加线性下降。利用KPFM测试手段首次在单层MoS2异质结中观测到光生载流子的产生和分离，证实了我们制备的这种超薄范德瓦尔斯异质能够实现电学功能。研究MoS2激子发光动力学以及谷极化、谷电子/自旋弛豫动力学过程，对MoS2二维层状原子晶体材料中丰富的有关激子和多体相互作用的物理过程，对CVD生长设备、空间与时间分辨、频谱与偏振分辨的微区实验测试系统进一步优化与升级。通过PL研究其发光特性，当二硫化钼从体材料变为纳米薄膜状态后，会出现光致发光的现象，其光致发光强度与二硫化钼薄膜的厚度成反比，利用基于AFM的压力电导平台测量了器件压力下电学性质的变化。