Fabrication and Electrical Characterization of Contacts to MoS2 and Oxidation-Based Growth Control

Abstract

Since the discovery of two-dimensional (2D) materials, transition metal dichalcogenides (TMDs) such as MoS₂ have garnered significant interest due to their unique electronic and optical properties. Unlike graphene, which lacks a bandgap, monolayer MoS₂ exhibits a direct bandgap, making it a promising candidate for next-generation electronic and optoelectronic applications. However, the controlled synthesis and reliable fabrication of metal contacts on MoS₂ remain key challenges in realizing scalable and reproducible device fabrication. This dissertation explores the fabrication of reliable metal contacts to optimize electrical performance in MoS₂-based devices and investigates the controlled oxidation of molybdenum via Joule heating for localized MoS₂ growth. The first study focuses on the electrical characterization of CVD-grown MoS₂ with both post-growth and naturally grown electrical contacts. By comparing different contact fabrication methods, we evaluate their impact on charge injection and contact resistance. Understanding these interactions is critical for optimizing MoS₂-based field-effect transistors (FETs) and other electronic devices. In the second study, we employ Joule heating to induce localized oxidation of metallic molybdenum, enabling patterned growth of MoS₂ via sulfurization. Our results reveal a power-dependent oxidation process, allowing precise control over the MoOx formation, which subsequently controls the growth characteristics of MoS₂. This method offers a scalable and deterministic approach to patterning 2D materials for large-area device applications. The third study explores the MoOx/MoS₂ interface synthesis and heterostructures through a controlled oxidation-sulfurization sequence. We successfully fabricate layered structures exhibiting distinct electronic behavior by tuning process parameters. Electrical measurements indicate strong interfacial interactions that modulate charge transport, suggesting their potential utility in tunable electronic and optoelectronic applications. This dissertation provides a comprehensive study of the growth and electrical characterization of MoS₂. The findings contribute to advancing 2D material integration in device applications by leveraging Joule heating for controlled oxidation and growth. Future work will focus on refining synthesis techniques, optimizing doping strategies, and exploring novel heterostructures to enhance device performance and functionality.