Ti/Ge2Sb2Te5/Ti thin films deposited by a sputtering method on SiO2/Si substrates were annealed at 400 degrees C in N-2 atmosphere and characterized by using transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) in order to investigate the inter-diffusion of the Ti/ Ge2Sb2Te5/Ti system due to annealing. The TEM and AES results showed that the interface between the Ti and the Ge2Sb2Te5 layers was unstable and Ti atoms were incorporated into the Ge2Sb2Te5 thin film upon annealing. The Te and Sb atoms of the Ge2Sb2Te5 layer diffused into the Ti layer. The intermixing layers between the Ge2Sb2Te5 layer and two Ti layers were formed. These results indicate that the microstructural properties of the Ti/Ge2Sb2Te5/Ti systems can be degraded by the postgrowth thermal annealing. (c) 2006 Elsevier B.V. All rights reserved.