Unraveling the Effect of Multiple Defect States in Synthetic Monolayer MoS₂ Through Electronic and Optical Probes

Two-dimensional transition metal dichalcogenides (2D TMDs) has been proven to be ideal for post-silicon technology. However, the intricacy and diversity of the defects in 2D TMDs affect the electrical and optical properties in many different ways, some of which even contradict to our intuition. Several challenging issues including Femi level pinning at metal/2D TMD interfaces, unintentional doping, and non-radiative excitonic recombinations, etc. have been attributed to a considerable amount of sulfur vacancy in monolayer MoS₂. On the other hand, specific types of defects, if controlled carefully, also offers the access to engineer the nature of monolayer MoS₂, such as intentional doping and exciton reservoirs to prolong the excitonic lifetime. Here, we explored the correlation between the domain shapes and the presence of different types of defects in monolayer MoS₂ grown by CVD through transport and spectroscopy measurements. Based on a two defect states model, the geometry-modulated behaviors of the MoS₂-metal band alignments, mobilities, and photoluminescence spectra could be explained simultaneously. This work not only offers a strategy to engineer the nature of MoS₂ from the synthesis perspective, but also pave a path to realize low-power MoS₂ CMOS integrated circuits.