Atomic Scale Structure and Defects in 2D GaSe Films and Van der Waals Interface

Recent advances in two-dimensional (2D) materials and interfaces have opened exciting new possibilities for realizing highly tunable electronic properties through innovative band gap engineering at the interface.2D materials can also be synthesized in a variety of compositions and structures, consequently resulting in novel properties at the interface that are not limited to the structural constraints in conventional interfaces, such as the choice of substrate and strain/defect control.Large area growth and/or transfer of 2D films have been extensively studied lately, most notably using metaldichalcogenides systems [1].Here, we present the cross-sectional atomic scale imaging and analysis of GaSe 2D layered materials on GaN substrate using scanning transmission electron microscopy (STEM) [2].Our analysis shows important details of the atomic structure that can dictate the electronic properties of GaSe and a new atomic scale reconstruction at the GaSe/GaN van der Waals (vdW) interface that has not been observed in any conventional epitaxy.Our new findings may have important implications for controlling the atomic structure of 2D/3D interfaces for tuning of the electronic structure at the interface for novel device applications.