Two-dimensional (2D) transition metal chalcogenide (TMDC) materials have been emerging as one central topic of the entire physical science and engineering.  These materials show remarkable excitonic properties and offer a tantalizing prospect of scaling all kinds of semiconductor photonic devices down to a truly atomic scale!  These include photodetectors, solar cells, LEDs, lasers, and optical modulators.

In this talk, I will first introduce a unique self-limiting chemical vapor deposition process that my groups has recently developed for the synthesis of high-quality centimeter-scale 2D MoS₂ with controlled layer numbers.  I will then demonstrate a unique surface energy-assisted transfer process developed in my group that can perfectly transfer the synthesized centimeter-scale films onto arbitrary substrates with no observable wrinkles and damages.  These capabilities of controlled scalable synthesis and transfer open up enormous unexplored opportunities for fundamental and applied research.

Of our most interest are the photophysics and photochemistry of 2D materials.  I will show our studies on the refractive index and catalytic activities of 2D MoS₂, both of which show a clear dependence on the layer number of 2D MoS₂.   Additionally, I will present our recent results on the excitonic dynamics in 2D heterstroctures that consists of multiple dissimilar monolayers epitaxially or non-epitaxially stacked in the vertical direction.   Our results indicate extremely efficient interlayer relaxation and transition of exictons in the 2D heterostructures. This suggests that 2D heterostructures may provide unprecedented capabilities to engineer excitons for the development of exotic photonic devices.