UC Riverside

The intense interest in graphene as the prototype 2D electronic material has recently been complemented by the investigation of layered transition metal dichalcogenides (TMD), notably MoS2 and MoSe2. These materials provide the favorable mechanical properties of graphene, but exhibit a direct bandgap without the need for nanostructuring, chemical functionalization, or the application of a strong electric field to bilayers. As a monolayer, MoS2 becomes a direct-gap semiconductor with a gap of 1.8 eV. In this dissertation, X-ray photoelectron spectroscopy (XPS), photoluminescence, spectroscopy and high-resolution angle resolved photoemission spectroscopy (ARPES) have been used to investigate monolayer and alloy thin films grown on various substrates. My research focuses on the thin film modification and characterization, composition analysis, low-energy argon ion sputtering process and bandgap tuning.