DEFECTS-MEDIATED OPTOELECTRONIC PROPERTIES OF MONOLAYER TUNGSTEN DISULFIDE

Abstract

Transition metal dichalcogenides (TMDs) stand out because of their intriguing semiconducting properties. However, abundant defects in TMDs strongly limit their applications. Understanding the behaviors of defects is essential to develop practical devices. The dissertation aims to find out the role of defects in optoelectronics and valley behaviors in CVD-synthesized WS2 monolayer. Initially, we discuss the effects of defects on electronic and optical properties from theoretical path, we provide deep insights into the corresponding experimental observations. Secondly, we systematically investigated the chemical and electronic density inhomogeneity of WS2 flakes. Our results highlight and unravel the significance of chemisorbed oxygen at the edges in the PL emission and electronic structure of WS2. Lastly, we discussed the valley properties of WS2 monolayer. An inversion relation between PL intensity and valley polarization was observed. Through the focused laser beam and electrical gating, we are able to tune the valley polarization of WS2 monolayer.