Influence of oxygen on the crystallization process in Ge: Sb:Te:O films

Ge:Sb:Te thin films have been studied extensively due to their application in phase-change optical memory technology. In this work Ge:Sb:Te:O films with oxygen in the range between 2 to 28 atomic %, are analyzed using X-ray diffraction and XPS measurements. The location of the oxygen in the structure of these films has been deduced from these measurements. Experimental results have shown that in films with oxygen content below 10 atomic %, Te, Sb and most of Ge are in metallic state and the free oxygen is located at the tetrahedral interstitial sites. In these films the oxygen acts as nucleation center in the process of crystallization. In films with higher contents of oxygen tellurium is in metallic state while some of the germanium and antimony form amorphous oxide and due to the deficit of germanium and antimony the amorphous films crystallized into the Sb₂Te₃ rhombohedral phase with the segregation of crystalline Te. From this characteristics GeSbTe-O can be used as active material in multi level optical memories