Hou Chao, Deng Jingwen, Guan Jianxin, Yang Qirong, Yu Zhihao, Lu Yilin, Xu Zihan, Yao Zefan, Zheng Junrong
College of Chemistry and Molecular Engineering, Beijing National Laboratory for Molecular Sciences, Peking University, Beijing 100871, China.
Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China.
Phys Chem Chem Phys. 2021 Nov 10;23(43):24579-24588. doi: 10.1039/d1cp03651c.
The low photoluminescence (PL) quantum yields of transition metal dichalcogenide monolayers have been a limiting factor for their optoelectronic applications. Various and even inconsistent mechanisms have been proposed to modulate their PL efficiencies. Herein, we use PL/Raman microspectroscopy and the corresponding mapping, atomic force microscopy, and field-effect transistor (FET) characterization to investigate the changes in the structural and optical properties of monolayer MoS. Relatively low power density (<4.08 × 10 W cm) of laser irradiation in ambient air can cause a slight PL suppression effect on monolayer MoS, whereas relatively high power density (∼1.02 × 10 W cm) of laser irradiation brings significant PL enhancement. Experiments under different atmospheres reveal that the laser-irradiation-induced enhancement only occurs in the atmosphere containing O and is more remarkable in pure O. In addition, physically adsorbed water can also induce PL enhancement of monolayer MoS. FET devices suggest that the adsorbed water produces a p-doping effect on MoS, and the laser irradiation in ambient air generates an n-doping effect, and both types of doping can enhance the PL intensity. The island-shaped defects caused by laser irradiation can be stabilized by oxygen atoms and act as trapping centers for excited trions or electrons, thus reducing the non-radiative recombination ratio and enhancing the PL intensity. The physically adsorbed water works in a similar way. A low power density of laser irradiation can sweep away the originally adsorbed HO on the surface, thus reducing the PL.
过渡金属二硫属化物单层的低光致发光（PL）量子产率一直是其光电应用的限制因素。人们提出了各种甚至相互矛盾的机制来调节它们的PL效率。在此，我们使用PL/拉曼显微光谱以及相应的映射、原子力显微镜和场效应晶体管（FET）表征来研究单层MoS结构和光学性质的变化。在环境空气中相对低功率密度（<4.08×10 W cm）的激光照射会对单层MoS产生轻微的PL抑制效应，而相对高功率密度（~1.02×10 W cm）的激光照射则会带来显著的PL增强。在不同气氛下的实验表明，激光照射诱导的增强仅发生在含有O的气氛中，在纯O中更显著。此外，物理吸附的水也能诱导单层MoS的PL增强。FET器件表明，吸附的水对MoS产生p型掺杂效应，环境空气中的激光照射产生n型掺杂效应，两种类型的掺杂都能增强PL强度。激光照射引起的岛状缺陷可以被氧原子稳定，并作为激发三重子或电子的俘获中心，从而降低非辐射复合率并增强PL强度。物理吸附的水以类似的方式起作用。低功率密度的激光照射可以扫去表面原本吸附的HO，从而降低PL。
