Modulation of electronic and optical properties of line defected armchair MoS₂ nanoribbon by vacancy passivation

In this study, the density functional theory (DFT) is used to investigate the effects of passivating line sulfur vacancies by non-metal species (C, N, O, F, OH and NH₂) in armchair MoS₂ nanoribbon (AMoS₂NR) on its structural, electrical and optical properties. Calculated binding energies show that passivation of line vacancies by oxygen atoms leads to the most stable structures. Electronic calculations show that presence of single line vacancies decreases the bandgap of 0.68 eV in perfect AMoS₂NR to 0.62 eV in single line vacant AMoS₂NR (SV) and substituting the vacancies with carbon and oxygen (C-SV and O-SV) returns the bandgap to its initial value. It is also shown that passivation of SV with NH₂ leads to a semiconductor with a small bandgap of 0.08 eV. However, substituting the vacancies of SV with N, F and OH results in metallic structures. In the case of double line vacant AMoS₂NR (DV), the bandgap reduces significantly (0.38 eV) with respect to its perfect counterpart. Similar to what happened in SV, passivating DV with C and O again increases the bandgap to the bandgap of the perfect structure. Furthermore, N-, F-, OH- and NH₂-DV show metallic behavior. In addition, we use total, projected and local density of states (TDOS, PDOS and LDOS) analysis to reveal the role of different atoms in different positions on the electronic properties of defective AMoS₂NRs. In order to investigate the effect of passivation on the optical properties of defective AMoS₂NRs we present the real and imaginary parts of dielectric function spectra. Our results suggest that passivation of line vacancies by different atoms can efficiently tune the absorption of AMoS₂NR and open a new path to obtain MoS₂-based optoelectronic devices. (paper)