HETEROEPITAXY OF GASE LAYERED SEMICONDUCTOR COMPOUND ON SI(111)7X7 SUBSTRATE - A VAN-DER-WAALS EPITAXY

In a conventional heteroepitaxial system, the misfit between the latti ce constants of two materials is a severe condition to overcome in ord er to get good heterostructures. Recently, Van der Waals epitaxy has b een shown to relieve the lattice-mismatch stress by using materials wh ich have strong bonding only in two dimensions. The Van der Waals epit axy has so far been limited to quasi-one- or quasi-two-dimensional mat erials. We report, for the first time, the epitaxial growth of a GaSe layered semiconductor on Si(111)7 x 7, a substrate that is known to ha ve active dangling bonds associated with the presence of adatoms along its surface. The film growth was performed by means of molecular-beam epitaxy and characterized in-situ by reflection high-energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS), and ex -situ by Raman spectroscopy and X-ray diffraction. It has been shown t hat the epitaxial growth was strongly affected by the growth condition s. At a low growth temperature range, multi-domains were observed. Thi s has been explained according to the film growth kinetics, in which t he nucleation and the growth are competing processes. At a high flux o f Se, a 3D growth was observed. It is related to the decrease of the s urface diffusion length of Ga adatoms. Finally, the mechanism for the epitaxial growth of GaSe on Si(111)7 x 7 is discussed in terms of the balance of surface free energy between interface, film and substrate.