Mechanism for heteroepitaxial growth of transparent p-type semiconductor: LaCuOS by reactive solid-phase epitaxy

A unique epitaxial growth method, reactive solid-phase epitaxy, was used to fabricate heteroepitaxial thin films of LaCuOS, a transparent p-type semiconductor with layered structure. The epitaxial growth mechanism is examined through microscopic observations. A thin metallic Cu layer deposited between the amorphous LaCuOS (a-LaCuOS) and the yttria-stabilized zirconia (YSZ) single-crystal substrate before thermally annealing is a key to realizing the epitaxial LaCuOS films in this process. To grow the epitaxial films, it is critical for the Cu layer to have a discontinuous structure with triple junctions among the Cu, a-LaCuOS layer, and the YSZ substrate. The Cu layer is needed to create seed grains for the epitaxial LaCuOS at the junctions. The resulting seed grains work as an epitaxy template for subsequent epitaxial growth from the substrate to the film's top surface, and high temperatures such as 1000°C are necessary to completely convert the a-LaCuOS layer to an epitaxial layer.