Xu Shujuan, Yang Jin, Jiang Huachao, Su Fuhai, Zeng Zhi
Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China. University of Science and Technology of China, Hefei 230026, People's Republic of China.
Nanotechnology. 2019 Jun 28;30(26):265706. doi: 10.1088/1361-6528/ab0f02. Epub 2019 Mar 12.
The frequency and time resolved conductivity in a photoexcited large-area monolayer tungsten disulfide (WS) have been simultaneously determined by using time-resolved terahertz spectroscopy. We use the Drude-Smith model to successfully reproduce the transient photoconductivity spectra, which demonstrate that localized free carriers, not bounded excitons, are responsible for the THz transport. Upon the optical excitation with 400 nm and 530 nm wavelength, the relaxation dynamics of the free carriers include fast and slow decay components with time constants approximately smaller than 1 ps and between 5-7 ps, respectively. The former sub-picosecond decay is attributed to the charge carrier loss induced by the exciton formation, while both the Auger recombination and the surface trapping can contribute to the slow relaxation.
通过时间分辨太赫兹光谱，同时测定了光激发大面积单层二硫化钨（WS）中的频率和时间分辨电导率。我们使用德鲁德-史密斯模型成功再现了瞬态光电导光谱，这表明局域自由载流子而非束缚激子是太赫兹传输的原因。在用400纳米和530纳米波长进行光激发时，自由载流子的弛豫动力学包括快速和缓慢衰减成分，时间常数分别约小于1皮秒和在5 - 7皮秒之间。前者的亚皮秒衰减归因于激子形成引起的电荷载流子损失，而俄歇复合和表面俘获都可能导致缓慢弛豫。
