This is a 1992 RIA Award. It is proposed to develop a new concept for fabricating hetero- interface systems using van der Waals surfaces of layered metal chalcogenide materials. This will be studied experimentally by growing different kinds of layered metal chalcogenides on top of each other by means of molecular beam epitaxy, a process that has been referred to as "van der Waals epitaxy". Of particular interest of this method is the ability to fabricate atomically and electronically abrupt hetero-interfaces without regard to their lattice matching requirement. The epitaxial conditions will be investigated in detail for improving the quality of the thin films, and the fundamental nucleation and growth of the epitaxial layers will be investigated. Due to the sensitivity of the layer stacking sequence to the properties of transition metal dichalcogenides, we will develop a technique to determine the "polytpism" of the growing thin film using Reflection High Energy Electron Diffraction oscillations. The unique nature of the hetero-interfaces fabricated by this method will allow the investigation of the fundamental aspects related to the electron transfer between metals and semiconductors, from which rational design of Schottky device structure will be explored. Finally the growth of selected semiconducting layered metal chalcogenide on GaAs will be investigated in a view toward the development of newer material systems. The potential flexibility for constructing complex layered heterostructures containing different materials selected for their specific material properties will constitute a substantial breakthrough in heteroepitaxy technology.
