OPTICAL AND OPTOELECTRONIC PROPERTIES OF 2D MATERIALS AND HETEROSTRUCTURES

Abstract

Two-dimensional (2D) materials show interesting electrical, optical, and optoelectronic properties. 2D material heterostructures hold some new properties not existing in a single 2D material. This thesis contains three interesting parts. In the first part, we use MoS2/BN/Au/SiO2 asymmetric Fabry-Perot cavity to enhance the absorption and to improve the optoelectronic device performance of monolayer MoS2. The maximum theoretical absorption of monolayer MoS2 at 532 nm is about 65.7% and photodiodes based on the cavity exhibit excellent current rectifying behavior, photo gain, and detectivity. In the second part, we investigate PL upconversion with an energy gain of 162 - 201 meV by defects in BN, which is attributed to one-photon and one-optical phonon absorption. Lastly, we tune the PL and Raman of MoS2/WS2 heterostructures by electrostatic doping. The out-of-plane Raman modes of both MoS2 and WS2 in the heterostructure become less sensitive to electron doping because of dielectric screening effect.