Thermal stability of Cr clusters on SrTiO3(100)

The thermal stability of ultrathin Cr overlayers on SrTiO3(100) was investigated by in situ reflection high-energy electron diffraction, X-ray photoelectron spectroscopy and scanning tunneling microscopy. The Cr was deposited by molecular beam epitaxy at room temperature, resulting in the formation of clusters. Heating cycles showed that the interaction and solid state reaction between metallic Cr clusters and SrTiO3 can be divided into three steps: Annealing of the clusters below 640 degreesC resulted in Ostwald ripening, transforming the initially randomly oriented clusters into clusters with the following well defined orientation relationship: (100)SrTiO3(100)Cr, [001]SrTiO3[011]Cr. At temperatures above 600 degreesC, oxygen bulk diffusion in SrTiO3 was activated, accompanied by the transport of oxygen ions across the Cr/SrTiO3 interface, resulting in the formation of an epitaxial chromium oxide phase. The oxidation process was accompanied by a morphological change of the clusters. At temperatures beyond 750 degreesC, interdiffusion of the Cr oxide clusters and SrTiO3 substrate was observed. (C) 2002 Elsevier Science B.V. All rights reserved.