Effects of Multiple Stacking Faults on the Electronic and Optical Properties of Armchair MoS _2 Nanoribbons: First-Principles Calculations

The electronic and optical properties of armchair MoS _2 nanoribbons with multiple stacking faults are investigated using first-principles calculations. It’s interesting that the band gaps approach zero for armchair MoS _2 nanoribbons with two and four stacking faults. The gaps of armchair MoS _2 nanoribbons with one stacking fault and three stacking faults are converged to 0.46 eV and 0.36 eV, respectively, which is smaller than perfect MoS _2 nanoribbons. The partial charge density of armchair MoS _2 nanoribbons with two stacking faults shows that the defect levels are originated from stacking faults. The frequency-dependent optical response (dielectric function, absorption, reflectance and electron energy loss spectra) is also presented. The optical results of monolayer MoS _2 are in agreement with previous study. The peaks in the imaginary part of perfect armchair MoS _2 nanoribbons are about 2.8 eV, 4.0 eV and 5.4 eV and the peaks of the imaginary part of armchair MoS _2 nanoribbons with stacking faults are mainly 2.8 eV and 5.4 eV. They are independent of ribbon width. The peaks in electron energy loss spectra move toward larger wavelengths (redshift) due to the introduction of stacking faults.