Temperature dependence of optical properties of monolayer transition metal dichalcogenides
Ya-Ting Chang1*, Cin-Wei Ye1, Chang-Lung Hsu2, Ming-Yang Li2, Sheng-Han Su2, Lain-Jong Li2, Hsiang-Lin Liu1
1Department of Physics, National Taiwan Normal University, Taipei, Taiwan
2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
* presenting author:張雅婷, email:22twchangyating@gmail.com
Spectroscopic ellipsometry was used to characterize the temperature dependence of optical properties of monolayer transition metal dichalcogenides. These thin films were grown on c-sapphire substrates using chemical vapor deposition. At room temperature, the extraordinary large value of the refractive index in the visible frequency range is obtained. The absorption response shows a strong correlation between the magnitude of the exciton binding energy and band gap energy. With increasing temperature, the refractive indices decrease apparently and the values of band gap and exciton binding energy show a redshift. The band gap narrowing coefficient of all thin films is in the range of 10-4 eV/K. These results provide the foundation for future technologically important developments of monolayer transition metal dichalcogenides-based optoelectronic devices.

Keywords: Monolayer transition metal dichalcogenides, Spectroscopic Ellipsometry