Roles of Oxygen in Crystalline GST and at the GST/TiAlN Interface

We present a first principles study of oxygen in crystalline Ge₂Sb2Te₄ and at the Ge₂Sb2Te₄/TiAlN interface. We find that oxygen molecules dissolve and dissociate exothermically into all of the crystalline forms of GST. Furthermore, we find that interstitial oxygen atoms are strongly attracted to the crystalline GST/TiAIN interface, where they bond preferentially between germanium and aluminum atoms. We have calculated energies of adhesion and we predict that single oxygen atoms increase significantly the adhesion of the GST film to the the metal.