Dimensionality is one of the most fundamental parameters that determine the physical characteristics of materials. This has been most strikingly highlighted over the last several years with two-dimensional (2D) graphene, which exhibits exotic condensed matter phenomena that are absent in bulk graphite. Discovery of graphene demonstrates that 2D crystals can exist in free-state contrary to earlier predictions that pure 2D structures would be unstable at nonzero temperatures. The ability to isolate atomically thin crystals from various layered compounds allows us to access and exploit physical characteristics of a variety of 2D systems.
Layered transition metal dichalcogenides (LTMDs) form a large family of materials that can be exfoliated to individual monolayers. Atomically thin sheets of Group 6 LTMDs such as MoS2 show unique thickness-dependent band structure that leads to indirect to direct gap crossover. While MoS2 is traditionally known as solid-state lubricant and catalyst, its 2D crystals hold promise in novel electronic, optoelectronic, spin- and valleytronic applications as well as provide access to fundamental physical phenomena. In this talk, I will discuss our recent findings on synthesis and geometrical confinement effects in some Group 6 LTMDs.