Date of Award

Spring 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering & Materials Science (ENAS)

First Advisor

Cha, Judy

Abstract

Over the last decade, significant progress has been made in studying topological materials whose wavefunctions possess a distinct topological invariant signature barring adiabatic deformation from a trivial phase to a non-trivial phase. There has been mounting experimental evidence for the presence of topological nature in nanomaterials due to their favorable surface-to-volume ratio and phase-coherent confinement. Considering that the material synthesis and transport measurement challenges must be overcome before topological nanomaterials can be used in next-generation electronic devices, in my dissertation, I focus on improving crystal quality and controlling dimensions of topological crystalline insulator SnTe in nanoscale as it provides a rich playground to examine interactions of correlated electronic states, such as ferroelectricity, topological surface states, and superconductivity. To develop facile strategies to suppress surface defects during chemical vapor deposition growth of SnTe nanostructures, we systematically investigate the origin and evolution of three-dimensional surface defects commonly observed on SnTe microcrystals and nanostructures. By employing alloy nanoparticles as growth catalyst, SnTe nanowires are synthesized with reduced diameters and high crystalline quality, such that one-dimensional confinement and phase coherence of the topological surface electrons can be ensured to probe the topological surface states. To further alleviate the high carrier density inside the bulk of SnTe nanowires and surface degradation, surface passivation of SnTe nanowires using in situ Te deposition during growth process is investigated. The material improvement approach in this dissertation aims to facilitate future research on understanding the extent of scattering of topological surface states due to crystalline defects, impurities, and coupling to bulk electron states.

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