Atomic and Electronic Properties of 2D Moiré Interfaces

Angebote / Angebote:

This thesis provides the first atomic length-scale observation of the structural transformation (referred to as lattice reconstruction) that occurs in moiré superlattices of twisted bilayer transition metal dichalcogenides (TMDs) at low (¿ < 2¿) twist angles. Studies using Scanning transmission electron microscopy (STEM) were limited due to the complexity of the (atomically-thin) sample fabrication requirements. This work developed a unique way to selectively cut and re-stack monolayers of TMDs with a controlled rotational twist angle which could then be easily suspended on a TEM grid to meet the needs of the atomically thin sample requirements. The fabrication technique enabled the study of the two common stacking-polytypes including 3R and 2H (using MoS2 and WS2 as the example) as well as their structural evolution with decreasing twist-angle.Also reported is a comprehensive investigation of electronic properties using scanning probe microscopy and electrical transport measurements of the artificially-engineered structures. These and other studies highlight the unique intrinsic properties of TMDs and their potential application in the development of the next generation of optoelectronics.