Electronic and Optoelectronic Properties of Two-Dimensional Heterostructures for Next-Generation Device Technologies

Since monolayer graphene was isolated in 2004, there has been significant interest in integrating layered materials into innovative device designs and hybrid materials to help solve pressing technological challenges. This is partially because they can typically be thinned to a two-dimensional (2D) form without suffering from roughness-induced scattering and can exhibit thickness-dependent variations in properties such as their energy band gap. This dissertation reports on investigations of electronic and optoelectronic device physics in 2D material heterostructures. The investigation of electronic device physics focuses on the interface between 2D molybdenum disulfide (MoS2) and gold (Au), which behaves as a resistive switching element (RSE). RSEs are microelectronic switches whose resistances depend on the history of electrical stimuli they have experienced. Prototype computer memory cells utilizing RSEs have demonstrated non-volatile switching behavior and high data retention times, likely enabling more environmentally-conscious computing. The ultimate degree of lateral scaling that MoS2-based RSEs can attain is currently unknown, but of great importance for determining their role in beyond-silicon computing applications. This work demonstrates, using the metallic tip of a scanning tunneling microscope as an electrode in a model MoS2-based RSE, that switching events can be recorded even in device areas on the order of tens of nanometers across without the use of lithographic techniques. The investigation of optoelectronic device physics focuses on utilizing hexagonal boron nitride (hBN), an electrical insulator with an ~ 6.0 eV band gap, to fabricate ultraviolet photodetectors. The main advantage that hBN-based detectors have over Si-based detectors is that they are inherently insensitive to visible and infrared light without needing bulky or expensive optical band pass filters, thus eliminating signal contamination from ambient sources. This work describes the fabrication and characterization of several detectors featuring vertical designs, allowing for greater degrees of both vertical and lateral scaling