Date of Award

Spring 2022

Project Type

Dissertation

Program or Major

Physics

Degree Name

Doctor of Philosophy

First Advisor

Shawna Hollen

Second Advisor

Kemp Plumb

Third Advisor

Jiadong Zang

Abstract

Due to their two-dimensional structure and wide range of electronic behaviors, van derWaals materials have garnered a lot of attention for new technological applications. However, much is still unknown about the consequences that impurities and disorder have on the performance of many new van der Waals materials. In my research I use scanning tunneling microscopy(STM) and electronic transport techniques to study the different types of disorder in three common van der Waals materials: tantalum disulfide (TaS2), black phosphorus (BP), and two-dimensional graphene. In TaS2 I show a sample preparation dependence on the surface state of the bulk crystal and emphasize the importance of this dependence. I also provide strong evidence that BP crystals are inherently p-doped with atomic vacancies, ending a long mystery as to the origin of the inherent sample doping. Finally, I show progress on metal-insulator transitions in graphene field effect transistors, as well as new techniques to characterize and analyze surface defects using STM.

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