The First Principles Calculation on the Raman Spectrum and Optical Properties of the Defect Monolayer MoS2

In the process of preparing monolayer MoS2 by chemical vapor deposition, the peak value of Raman spectrum will be different due to the thickness of deposited film. After irradiated by fast neutron, the two modes of E-2g and A(1g) in the Raman spectrum of MoS2 are red shifted and broadened, and a new peak appears near 440-460 cm(-1) (Tang. G, Pam. M. E, Zhang. H, et al. Applied Physics Express. 12(5), 056,001 2019). In this paper, two types of defects are constructed and their Raman spectra are calculated by first principles. To compare with the experimental Raman spectra of monolayer MoS2, we confirm the defect configurations in the experiment. Through the calculation of optical properties of monolayer MoS2 with defects, the calculation results show that the imaginary part of the dielectric function of ideal monolayer MoS2 has a high intensity peak near 3.0 eV, and the imaginary part of the dielectric function of the defect monolayer MoS2 also has a peak of the similar shape; due to the localized effect of vacancy defects, the peak value appears a little red shift. A new peak value of the imaginary part of the dielectric function of the monolayer MoS2 with molybdenum vacancy defects appears near 0.6 similar to 1.2 eV.