Mary Blankenship, M.S. Candidate

Department of Chemistry and Biochemistry

Investigation of the chemical and electronic structure of a 2H phase MoS2 single crystal

Committee Members:

• Dr. Clemens Heske, Advisory Committee
• Chair Dr. Dong-Chan Lee, Advisory Committee Member
• Dr. Balakrishnan Naduvalath, Advisory Committee Member
• Dr. Joshua Island, Graduate College Representative

Abstract

• MoS2 has a wide range of applications in energy conversion devices like thin-film solar cells, as well as batteries, bio-sensors, and more. Although the properties of MoS2 and other transition metal dichalcogenides (TMDC) have been widely studied, disagreements and discrepancies regarding its electronic structure remain. In this thesis, a highly-oriented synthetic 2H phase MoS2 single crystal is investigated using a toolchest of spectroscopic techniques to uncover the chemical and electronic properties. Labbased x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), inverse photoemission spectroscopy (IPES), and low energy electron diffraction (LEED) was measured at UNLV and combined with resonant inelastic x-ray scattering (RIXS) at the Advanced Light Source (ALS), Lawrence Berkeley National Laboratory. Together with theoretical calculations of the density of states and band structure, an in-depth picture of MoS2 properties is painted. In addition, the effects of mechanical exfoliation on the chemical and electronic environment of the MoS2 crystal surface is discussed. The results are compared to past studies and the established knowledge of the electronic structure of MoS2.