Ba0.5Sr0.5TiO3, indium tin oxide (ITO), ZnO, and ZrO2 thin films were grown directly on Si substrates by the pulsed laser deposition technique. X-ray photoelectron spectroscopy investigations showed that these films contain oxygen species that are loosely bound, corresponding to what can be described as physisorbed oxygen. This oxygen is responsible for the formation of an interfacial layer at the interface between the Si substrate and the deposited oxide layer during the deposition process. The chemical composition of this interfacial layer consists of SiOx partially mixed with the grown oxide. The trapped oxygen can ensure further growth of the interfacial layer during any post-deposition anneals even when performed in vacuum or inert atmospheres. (C) 2002 Elsevier Science B.V. All rights reserved.