Elimination of S Vacancy as the Cause for the n-Type Behavior of MoS2 from the First-Principles Perspective

Molybdenum disulfide (2H-MoS2) based low-dimensional nanostructure materials have great potential for applications in electronic and optoelectronic devices. However, some of the properties such as the origin of the native n-type electrical conductivity (EC) observed in these materials still remain elusive. Here, the defect properties in the 2H-MoS2 bulk system are systematically investigated by first-principles calculation to address these issues. We find that the S vacancy V-S with low formation energy cannot be the origin of n-type EC owing to its deep defect levels within the valence band region. All other donor defects such as antisite Mo-S or Mo interstitial Mo-I also have deep levels that can trap electrons leading to depressed EC. S-Mo and S-I could be the origin of the p-type EC in 2H-MoS2, but the concentrations are expected to be rather low due to their high formation energies and can only be enhanced under S-rich/Mo-poor conditions. These results provide the underlying insights on the defect properties 2H-MoS2 and explain well the experimental observations.