3 - Electronic and electromechanical properties of vertical and lateral 2D heterostructures

Abstract

To increase the range of functionality afforded by two-dimensional (2D) materials, research has progressed in the direction of creating and investigating stacked assemblies of 2D materials, or heterostructures. The stacking can occur in the direction normal to their plane (vertical heterostructures) or, via ingenious synthesis techniques, in the same plane—thereby yielding in-plane heterostructures or domain superstructures. The range of properties of both vertical and in-plane heterostructures depends on a variety of factors, but primarily on the properties (electronic, mechanical, piezoelectric, etc.) of the specific component 2D materials, as well as on the possible lattice constant differences between adjacent 2D layers. Herein, we explore piezoelectric properties of vertical and in-plane heterostructures created from transition metal dichalcogenide layers (TMDC in vertical heterostructures) and graphene and hexagonal boron nitride (in-plane domains and ribbons). For TMDC heterostructures, we use density functional theory calculations to explore the effects of stacking registry and of specific layers on the electronic bandgap and on piezoelectric properties. We also present a brief review of hybrid domains (in-plane) in terms of their synthesis, mechanical, and electronic properties. As experimental efforts become increasingly successful in terms of controlling the morphology, composition, stacking, and relative dimensions of various heterostructures, the results presented here could provide guidance for targeted synthesis or assembly of materials with properties useful for nanoscale device applications.