Defect Properties in MoS2 Structure as 2D Material Gas Sensor

Abstract

Electronic properties of 2D materials are sensitive to changes at surface, which provides an opportunity for toxic gas sensors requiring high sensitivity. Changes at surface include surface defects and gas molecule adsorbates often trapped at special sites. To understand the role and impact of such trapping sites in sensing mechanism, various point defects on molybdenum disulfide (MoS2, 2D semiconductor) are studied using density functional theory (DFT). DFT+U method is used to recover the experimental bandgap energy of MoS2, indicating strong electron correlation effect. Preliminary studies found that Sulfur vacancy shall assume negative (positive) charges near conduction (valence) band. Such charged defects compensate electron and hole carriers, lowering the carrier density. Furthermore, the charged defects will behave as sources of strong Coulomb scattering, hampering electron mobility. Therefore, sulfur vacancy itself found to degrade the efficiency of 2D gas sensor made of MoS2. The role of sulfur vacancy for gas molecule absorbate along with the electronic property of the vacancy-absorbate complex need to be further studied to comprehend the overall impacts played by sulfur vacancy in MoS2 gas sensor.