Department of Chemistry and Physics, School of Natural Science, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea.
Nanoscale. 2017 Aug 3;9(30):10647-10652. doi: 10.1039/c7nr01834g.
Due to its unique layer-number dependent electronic band structure and strong excitonic features, atomically thin MoS is an ideal 2D system where intriguing photoexcited-carrier-induced phenomena can be detected in excitonic luminescence. We perform micro-photoluminescence (PL) measurements and observe that the PL peak redshifts nonlinearly in mono- and bi-layer MoS as the excitation power is increased. The excited carrier-induced optical bandgap shrinkage is found to be proportional to n, where n is the optically-induced free carrier density. The large exponent value of 4/3 is explicitly distinguished from a typical value of 1/3 in various semiconductor quantum well systems. The peculiar n dependent optical bandgap redshift may be due to the interplay between bandgap renormalization and reduced exciton binding energy.
由于其独特的层数依赖的电子能带结构和强激子特性，原子层厚的 MoS 是一个理想的二维体系，可以在激子发光中检测到有趣的光激发载流子诱导现象。我们进行了微光致发光（PL）测量，观察到在单层和双层 MoS 中，随着激发功率的增加，PL 峰发生非线性红移。发现光致自由载流子密度 n 的增加与光致带隙收缩成正比。这个大的指数值 4/3 与各种半导体量子阱系统中的典型值 1/3 明显不同。这种特殊的 n 依赖的光学带隙红移可能是由于带隙重整化和减小的激子束缚能之间的相互作用。
