Study of the growth of supported Pd–Sn bimetallic nanoclusters

Pd–Sn bimetallic thin films were grown by molecular beam epitaxy on KCl (001) single-crystalline substrate. Substrate and deposit crystallographic structures were studied by reflection high-energy electron diffraction (RHEED). Evolution of lattice parameter and cluster size calculated from the RHEED patterns gave information on the formation of bimetallic system. The early stages of the growth in dependence of Pd and/or Sn deposition sequence were studied. The formation of Pd–Sn core-shell structure was observed. It is composed of (001) epitaxialy oriented Pd core clusters surrounded by polycrystalline Sn and/or Pd–Sn shell. The Auger electron spectroscopy (AES) induced by high-energy electron beam and electron energy loss spectroscopy (EELS) were used as auxiliary methods for chemical analysis. Encapsulation of metallic clusters by the material of the substrate was approved by diffraction as well as by electron spectroscopy methods. This phenomenon influenced the formation of Pd–Sn bimetallic system.