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Nano Letters, 2014.
Yuxuan Lin *†, Xi Ling †, Lili Yu †, Shengxi Huang †, Allen L. Hsu †, Yi-Hsien Lee ¶,Jing Kong †, Mildred S. Dresselhaus *†§, and Tomás Palacios *†
† Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
¶ Material Sciences and Engineering,National Tsing-Hua University, Hsinchu, 30013, Taiwan
§ Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
ABSTRACT
Photoluminescence (PL) properties of single-layer MoS2 are indicated to have strong correlations with the surrounding dielectric environment. Blue shifts of up to 40 meV of exciton or trion PL peaks were observed as a function of the dielectric constant of the environment. These results can be explained by the dielectric screening effect of the Coulomb potential; based on this, a scaling relationship was developed with the extracted electronic band gap and exciton and trion binding energies in good agreement with theoretical estimations. It was also observed that the trion/exciton intensity ratio can be tuned by at least 1 order of magnitude with different dielectric environments. Our findings are helpful to better understand the tightly bound exciton properties in strongly quantum-confined systems and provide a simple approach to the selective and separate generation of excitons or trions with potential applications in excitonic interconnects and valleytronics.
