The Effect of Sulfur Vacancy Distribution on Charge Transport across MoS2 Monolayers: A Quantum Mechanical Study.

Abstract

Molybdenum disulfide (MoS₂) monolayers are two-dimensional materials belonging to a family of materials called transition metal dichalcogenides which have been widely studied as potential semiconductors for next-generation ingredients in transistor technology. Electronic devices' performance is largely influenced by defects, and in the case of MoS₂, the most dominant defects are sulfur vacancies. The correlation between charge transport across MoS₂ and sulfur vacancies is complex and not trivial, and it is still unclear how the distribution of vacancies influences electronic conductivity. In this study, MoS₂ monolayers with various sulfur vacancies concentrations and distributions were examined using density functional theory for electronic structure properties, tight-binding (TB) theory to construct the TB Hamiltonian, nonequilibrium Green's function formalism for transmission function calculations, and Landauer-Büttiker formalism for calculating charge transport. In addition, we employed design of experiments analysis to identify important structural features influencing the calculated current and to fit an empirical model to the results. We found that higher vacancy concentrations lead to a significant increase in electron permeability, with the best results occurring when sulfur vacancies were arranged in lines with alternating presence across both layers. The ability to predict charge transport across MoS₂ monolayers based on sulfur vacancy distribution can assist in the design of functional materials with desired properties, aiming to selectively apply structural defects.