过渡金属硫化物二维单层半导体纳米材料超快时间分辨动力学性质研究

The transition metal dichalcogenides (TMDC) 2-Dimensional monolayer materials have been an emerging field in the investigation on layered ultrafast semiconductor optoelectronics and drawn much attention in recent years. The project aims at typical TMDC 2D mono- and few-layer semiconductor materials, in combination with liquid exfoliation technique for high cleanliness and high quality micro or sub-micro sized sample, ultrafast time-resolved two color beam micro pump-probe system, time correlated single photon counting technique, high spatial resolution confocal micro spectra detection technique, to analyze the relationship between layer number, element type, substrate and photoluminescence lifetime, carrier mobility, diffusion coefficient, etc. and thoroughly study the photo induced dynamics properties and find the congener characteristics under external modulations such as temperature, the excitation wavelength and intensity. Supported by theoretical simulation, the physical mechanisms of dynamics like ultrafast carrier relaxation in TMDCs are expected to be clearly clarified. The carrier dynamics depends directly on the layer number, the perfection of lattice and the composition of the material. It is significant to realize precise measurement of carrier mobility, the lifetime of exciton, the diffusion rate, etc., in mono- and few-layer TMDCs and obtain a deep understanding of various novel physical phenomena induced by two dimensional quantum confinements for the development of micro-planar ultrafast optoelectronic devices in future.

过渡金属硫化物二维单层材料作为层状半导体超快光电子学研究的新兴领域备受人们关注。本项目以典型过渡金属硫化物二维单层及寡层半导体材料为研究载体，采用液相剥离技术制备具有清洁度高、尺寸在微米/亚微米量级的高质量单层及寡层单体，利用超快时间分辨双色显微泵浦-探测系统、时间关联单光子计数技术、空间高分辨共焦显微光谱探测技术，分析样品层数、元素类型、基底与荧光寿命、载流子迁移率、扩散系数等的依赖关系，深入研究在温度、激发光波长、强度等外加条件调制下微纳层状半导体的光动力学性质和同族变化规律，结合理论拟合，阐明过渡金属硫系化合物超快载流子弛豫等动力学过程的物理本质。二维体系的层数、晶格完整性和材料组成直接决定其载流子动力学行为，实现单层及寡层载流子迁移率、激子寿命、载流子扩散速率等的精确测量并深入理解二维限制效应所诱发的各种新奇物理现象，对未来微平面超快光电子器件的开发应用具有非常重要的意义。

二维层状结构和量子限制效应使过渡金属硫化物半导体具有独特的光电子学性能，基于该体系的纳米光电器件已成为信息领域的重要研究前沿之一。张赛锋及其团队在国家自然科学青年基金项目支持下，结合激光技术和纳米技术，系统开展了以WS2, MoS2为代表的层状过渡金属硫化物二维纳米半导体的超快非线性光学，特别是三阶非线性光学和光学非参量过程的研究工作，1) 实现了寡层半导体中共振态和非共振态双光子吸收及饱和吸收的“开-关”操作，为禁带宽度大于光子能量的二维半导体的锁模和调Q特性提出了一种新的物理机理；2) 利用快慢饱和吸收模型获得了MoS2，石墨烯，黑磷的基态与激发态吸收截面，阐明了该类材料作为优良饱和吸收体的物理机理；3）制备了晶片尺寸MoS2复合薄膜并成功应用到超快饱和吸收体这类锁模器件。.在过渡金属硫化物的材料制备、非线性特性、光子器件等方面取得多项原创研究成果。在本项目支持下，共发表第一作者论文3篇，通讯作者2篇，合作作者6篇，其中影响因子大于3的10篇，包括ACS Nano一篇 (IF=13.334)、Nature Communications一篇(IF=11.33)、Nanoscale 4篇(IF= 7.76)、Applied Physics Letters 1篇(IF=3.14)等。其中，发表在Nature Communications [6, 8563, 1-11(2015).]论文被SCI基本科学指标ESI评为热点论文“Hot paper”；发表在Nanoscale [7, 2978 (2015)]论文，被遴选为2015年度热点论文“Hot paper”。获国际会议邀请报告1次，国际会议口头报告2次，国内会议口头报告2次，专利3项。.