Synthesis of two-dimensional van der waals superlattices, heterostructures, and alloys from conversion of sequentially layered sub-nanometer metal films

Abstract

Manipulation of bulk material properties by controlling layer-by-layer chemistry and structure of nanomaterials has remained an overarching goal of nanoscience and nanoengineering. In the case of two-dimensional (2D) materials, heterostructures consisting of different compositions, stacking, and orientation can serve as a platform for designing bulk material properties; however, fundamental challenges associated with materials processes have limited material quality and impeded scalability. Most attempts to overcome this limitation have relied on slow layer-by-layer growth or meticulous transfer of grown single layers. Our work describes a method to directly convert easily fabricated sub-nanometer metal multilayer heterostructures on both sapphire and SiO2 substrates followed by conversion to 2D van der Waals superlattices, heterostructures, and alloys. These materials exhibit novel bulk properties compared to individual 2D layers themselves including reduced bandgap, enhanced light-matter coupling, and improved catalytic performance. The process versatility enables tunable orientation, layer structure, and chemistry in an exciting class of 2D nanomaterials and provides an opportunity to generate a wide range of artificially stacked multicompositional 2D structures with controlled morphologies.