On the growth process of a layered material on a covalent substrate: GaSe/Si

Abstract

The atomic structures of epitaxial deposits of GaSe on Si(1 1 1), involving 1.5, 2.5, and 10 Ga 2Se 2 sheets, were derived from grazing incidence X-ray diffraction. GaSe is a two-dimensional (2D) compound, characterized by iono-covalent sheets, bound to each other by van der Waals interactions. It is relevant to analyze the relief of the constraints in the epitaxy of such 2D structure on a 3D substrate, in comparison with the 3D–3D case. Our models imply sheets stacked in a (1 1 1) FCC way, two orientations at 180° developing. Some domains remain strained with Si, while some are laterally relaxed. The latter could act as a strain relief for two adjacent strained parts. The growth proceeds by complete sheets, preferably on those laterally relaxed, leading to steps on the final surface, at least of 8 Å height.