Dissertation Talk: Understanding and Engineering the Surface and Edge Defects of Transition Metal Dichalcogenides

Presentation: Dissertation Talk: EE | May 7 | 521 Cory Hall

 Peida Zhao, EECS

 Electrical Engineering and Computer Sciences (EECS)

Two dimensional (2D) semiconductors, a family of layered materials, possess interesting properties from van der Waals layer-to-layer interaction, excitonic carrier interactions, to layer dependent band structure and band gap. With great potential in various electronic and optical applications, these 2D materials unfortunately also suffer from various surface and edge defects.

In this talk, I will discuss work done in both understanding and engineering the surface and edge defects of 2D materials. A material characterization study of exfoliated WSe2 will be shown, along with a method for surface covalent functionalization which induces controllable and stable degenerate doping. In addition, edge defects present in monolayer WS2 will be discussed and characterized, when the monolayer lateral size becomes comparable to the excitonic diffusion length. A metric quantitatively describing the edge quality will be introduced. Finally, this metric is extended to 4 relevant 2D materials (WSe2, WS2, MoS2, and MoSe2) while utilizing a scanning probe-based lithography technique for patterning.

 pezhao@berkeley.edu