Spectroscopic photoemission and low-energy electron microscopy studies of the surface and electronic structure of two-dimensional materials

Abstract

Advances in two-dimensional (2D) materials research have opened up new opportunities in miniaturization of optoelectronic and spintronic devices at the atomically thin limit. One major research thrust, which is the subject of this review, is the surface- and electronic structure of 2D materials and their van der Waals (vdW) heterostructures that may be significantly affected by the local atomic geometry and environment. As a result, there is a pressing need for powerful advanced microscopy and spectroscopy techniques for material characterization at a micro- or sub-micrometer lateral scale, which is a typical sample size in many 2D-materials experiments. Spectroscopic photoemission and low-energy electron microscopy (SPE-LEEM) offer a multifunctional approach that uniquely integrates microscopy, diffraction and spectroscopy techniques, enables real-time imaging and in situ structural, chemical and electronic analysis of surfaces and interfaces. This review covers the recent developments in SPE-LEEM investigations of surface- and electronic structure of 2D materials, and presents examples including exfoliated vdW layered materials, vdW heterostructures, and thin films synthesized by chemical vapor deposition and molecular beam epitaxy.

Keywords

• two-dimensional materials
• surface
• electronic structures
• photoemission spectroscopy
• electron microscopy