Substrate Effects on The Nucleation and Growth of GaSe Layers by Van Der Waals Epitaxy

Abstract

Epitaxial thin film multilayers are limited by the need for both lattice and thermal expansion matching. Recently, a new deposition technique, known as van der Waals epitaxy, has been developed to overcome these limitations. Van der Waals Epitaxy (VDWE)promises the ability to deposit multilayers based on the property of interest without being limited by lattice and thermal expansion mismatch. The crystallographic two dimensional metal chalcogenides are characterized by strong covalent bonding within a layer and weak van der Waals bonds between layers. By combining the layered nature of the metal chalcogenides with other layered materials as well as crystallographic 3D materials, oriented single crystal layers can be deposited, resulting in novel structures with atomically abrupt interfaces. However, even with the weak van der Waals bond, substrate/film interactions play a large role in the final structure.

To study the substrate/film interaction occurring during van der Waals Epitaxy growth on 3D surfaces, the metal chalcogenide GaSe has been systematically deposited on GaAs(1 11) substrates. To develop an understanding of the interaction of the substratewith the growing film, growth of GaSe on both atomically rough and smooth substrates was studied. Comparison of the information developed through RHEED, TEM and AFM have been used to understand the basic nucleation and growth process as well as the observation and formation of film defects.