Review of optical properties of two-dimensional transition metal dichalcogenides

Two dimensional (2D) materials have become a growing subject in the last 15 years mainly due to the isolation of graphene, which created a completely different class of material based on its unique, monolayer design. Since then, various stable materials of few atoms thick are showing emerging capabilities in optical electronics and photonics. Semiconducting monolayers of transition metal dichalcogenides (TMDs) such as MoS 2 , Mo 1-x WxS 2 , and WS 2 exhibit direct electronic band gaps; bulk crystals display indirect band gaps. Interestingly, these 2D materials show significant light interaction over a broad bandwidth ranging from infrared to ultraviolet wavelengths. The materials allow photodetection in this bandwidth without the need of cooling, thus creating new potential for uncooled detection. In this review, we discuss various 2D materials and their interaction with light for photodetection applications.