单层、少层和垂直竖立多层MoS2/Si异质结构材料的制备、表/界面调控及光电特性研究

The graphene-like two dimensional layered MoS2 possesses a unique microstructure, optical and electrical property. Monocrystal silicon is an excellent semiconductor and optoelectronic functional material with mature and stable processing technology. Architecture of MoS2/Si heterojunction is a synergistic combination of the attractive properties of the both materials and is expected to be used in the next generation high-performance photovoltaic or optoelectronic devices. However, the present study is limited to characterizing and comparing the photovoltaic or optoelectronic properties of these heterojunctions prepared by different methods, while the electronic structure, carrier transport and photo-electronic interactions at the heterojunction interfaces still lack intensive study. This proposal is to prapare high quality, large size monolayer, few layers, and vertically standing layered MoS2 films on silicon substrate by chemical vapor deposition (CVD) technique and magnetron sputtering technique, respectively. Firstly, the preparation parameters, the modulating methods of the surface and interface, and the lateral photovoltaic effects will be investigated; then the interfacial constitution between the MoS2 and the Si will be investigated and the chemical bonding relationship is expected to be acquired; thirdly, the heterojunction contact barrier height, electrical transport property and their relationships with MoS2 layers, morphology, doping, defects of surface and interface, conducting type of substrate, and transparent conducting layers will be measured; finally, the optoelectic properties will be investigated detailly and the physical mechanism of MoS2-modulated photovoltaic effect of MoS2/Si heterojunction is expected to be proposed. The research output of this proposal will be fundamentally important aiming for design and development of Si-based MoS2 high efficiency photovoltaic and optoelectric devices.

类石墨烯二维层状MoS2原子晶体材料具有独特的微观结构、光学和电学性质，单晶硅是一种优异的半导体和光电功能材料，且工艺成熟和稳定，制备出高质量MoS2/Si异质结能够发挥两者协同效应，有望在高性能光伏或光电子器件中实现重要应用。然而，目前的研究仅限于不同方法和工艺制备异质结性能的表征和对比，对于异质结表/界面上的电子结构、载流子输运以及光电相互作用尚缺乏深入的研究和认识。本项目拟以CVD和磁控溅射技术分别在单晶硅衬底上制备（或转移）大面积高质量单层、少层和垂直竖立多层MoS2/Si异质结构，通过工艺参数摸索、表/界面调控及光电性能的研究，揭示异质结表/界面处的原子排列方式，探明MoS2层数、形貌、掺杂、表/界面缺陷态、衬底导电类型以及透明导电层和电极层的引入等条件对异质结电学和光电性能的影响，并阐明其物理机制，为进一步设计开发单晶硅基MoS2异质结构光电子和光伏器件提供理论和实践上的依据。

类石墨烯二维层状MoS2原子晶体材料具有独特的微观结构、光学和电学性质，单晶硅是一种优异的半导体和光电功能材料，且工艺成熟和稳定，制备出高质量MoS2/Si异质结能够发挥两者协同效应，有望在高性能光电子学器件中实现重要应用。另外，对于之前报道的MoS2主要为平行层状的单层或少层结构，其优异的光吸收性能不能得到很好的发挥。虽然增加层厚在一定程度上可以提高光吸收，但是其异质结载流子在纵向方向上又属于层间传输，性能较差。因此，如果能够制备出垂直取向层状结构的MoS2将同时发挥其强的光吸收和优异的载流子层内输运性能，从而具有重要研究意义。本项目分别以CVD和磁控溅射法研究了单晶Si衬底上制备大面积高质量垂直竖立少层和多层MoS2薄膜的制备工艺，并且对其异质结的光电和侧向光伏效应进行了系统表征和分析：（1）利用CVD法在Si/SiO2衬底上制备出大面积垂直竖立少层MoS2纳米片，结晶质量很高，层厚约5-7个原子层，各原子晶格排列完美；将薄膜转移至单晶Si衬底后形成高质量MoS2/Si异质结，并分别构筑了光电探测器和光位置灵敏探测器；该光电探测器的光响应度和检测度分别达到908.2 mA/W和1.889×10^13 Jones，同时响应速度达到空前的56/825 ns；而该光位置灵敏探测器的最高灵敏度为401.1 mV/mm，响应速度为16/176 ns，更为重要的是根据侧向光伏效应特殊的工作原理揭示出MoS2层内传输速度为5 ns，层间速度为11 ns。（2）利用磁控溅射法直接在单晶Si片上制备出大面积垂直竖立多层MoS2/Si异质结，对其侧向光伏响应进行了系统研究，侧向光电压和光电流灵敏度分别达到391.1 mV/mm和285.2 μA/mm，而且保持极好的非线性度（<2%）；另外，还在该结构中开发出侧向光电阻效应，并从理论上进行了分析和解释。（3）通过在磁控溅射法制备垂直竖立多层MoS2表面修饰一层CsPbBr3量子点，降低了其表面活性并提高了光吸收，使得MoS2/Si异质结的光电探测性能得到显著提升。该项目研究揭示了MoS2层结构、形貌和表/界面调控等对其异质结光电性能的影响和相关机制，为进一步设计开发单晶Si基二维异质结器件提供了重要实验和理论依据。