Advances in Two-dimensional Materials Research using Aberration-corrected Transmission Electron Microscopy

Abstract

Background and Objectives: Aberration-corrected transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) are indispensable tools for the study of two-dimensional (2D) materials. The utilization of aberration correctors enables comprehensive investigations into the defects, structure, growth, and properties of atomically thin materials at atomic scale. Methods: In this context, recent advances in atomic-resolution TEM and STEM include the in-depth study of 2D materials. Results: Firstly, hexagonal boron nitride (hBN) is an insulating 2D material with a large bandgap. My research group discovered that the twin boundary is composed of a 6′6′ configuration, which exhibits a conducting feature with a zero bandgap. This is an ultimately one-dimensional hBN conducting channel. This presentation addresses the growth of zinc oxide (ZnO) monolayers on graphene and graphene oxide substrates. My group demonstrated the atom-by-atom growth of zinc and oxygen at the preferential zigzag edge of a ZnO monolayer on graphene through in situ TEM observation. In the case of a graphene oxide substrate, the spontaneous formation of a ZnO monolayer was successfully achieved. The spontaneous oxidation of deposited Zn metal with the consumption of oxygen-containing functional groups on graphene oxide provides a reliable source of oxygen. Experimental determination revealed that the thinnest ZnO monolayer possesses a wide band gap, a consequence of its graphene-like structure and high optical transparency. In addition, the formation and analysis of the F-diamane structure, the thinnest diamond layers, will be presented. Discussion and Conclusion: Furthermore, recent studies on 2D materials will be discussed with reference to in situ TEM techniques.