RHEED and XPS study of Pd–Sn bimetallic system growth

An early stage of Pd–Sn bimetallic system growth on highly oriented pyrolytic graphite HOPG(0 0 0 1) was observed by means of reflection high energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS). Both metals were deposited using a molecular beam epitaxy under the UHV conditions. RHEED measurements were performed in real-time during all stages of the experiment. Metal clusters’ growth exhibited strong dependence on metals’ amount, succession of deposited materials and substrate conditions during the deposition. At very low coverages, the epitaxial as well as the polycrystalline phases of tin were observed. With increasing amount of deposited tin, the epitaxial phase became dominant. Palladium depositions with the substrate held on elevated temperature exhibited epitaxial growth. Metallic clusters of both metals grew in Volmer–Weber mode. The formation of Pd–Sn alloy was observed under the specific preparation procedure and was confirmed by both structural and chemical analysis.