Kim Ho-Jong, Yun Yong Ju, Yi Sam Nyung, Chang Soo Kyung, Ha Dong Han
Quantum Technology Institute, Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea.
Department of Physics, Yonsei University, Seoul 03722, Republic of Korea.
ACS Omega. 2020 Apr 3;5(14):7903-7909. doi: 10.1021/acsomega.9b04202. eCollection 2020 Apr 14.
Various postsynthesis processes for transition metal dichalcogenides have been attempted to control the layer number and defect concentration, on which electrical and optical properties strongly depend. In this work, we monitored changes in the photoluminescence (PL) of molybdenum disulfide (MoS) until laser irradiation generated defects on the sample flake and completely etched it away. Higher laser power was required to etch bilayer MoS compared to monolayer MoS. When the laser power was 270 μW with a full width at half-maximum of 1.8 μm on bilayer MoS, the change in PL intensity over time showed a double maximum during laser irradiation due to a layer-by-layer etching of the flake. When the laser power was increased to 405 μW, however, both layers of bilayer MoS were etched all at once, which resulted in a single maximum in the change of PL intensity over time, as in the case of monolayer MoS. The dependence of the etching pattern for bilayer MoS on laser power was also reflected in position changes of both exciton and trion PL peaks. The subtle changes in the PL spectra of MoS as a result of laser irradiation found here are discussed in terms of PL quantum efficiency, conversion between trions and excitons, mean interatomic spacing, and the screening of Coulomb interaction.
人们尝试了各种过渡金属二硫属化物的合成后处理方法来控制层数和缺陷浓度，而电学和光学性质强烈依赖于这些因素。在这项工作中，我们监测了二硫化钼（MoS）的光致发光（PL）变化，直到激光辐照在样品薄片上产生缺陷并将其完全蚀刻掉。与单层MoS相比，蚀刻双层MoS需要更高的激光功率。当在双层MoS上激光功率为270 μW且半高宽为1.8 μm时，由于薄片的逐层蚀刻，PL强度随时间的变化在激光辐照期间呈现出双最大值。然而，当激光功率增加到405 μW时，双层MoS的两层会一次性被蚀刻掉，这导致PL强度随时间变化出现单一最大值，就像单层MoS的情况一样。双层MoS蚀刻图案对激光功率的依赖性也反映在激子和三重激子PL峰的位置变化上。本文从PL量子效率、三重激子与激子之间的转换、平均原子间距以及库仑相互作用的屏蔽等方面讨论了此处发现的激光辐照导致的MoS的PL光谱的细微变化。
