Layer intermixing during metal/metal oxide adsorption: Ti/sapphire(0001)

First principles density functional calculations for adsorption of Ti on Al2O3(0001) indicate that Ti:Al2O3(0001) interfaces become intermixed. Substitutional Ti replaces a surface Al atom rather than a subsurface Al, and the Al-terminated surface is unstable under Ti adsorption. Adsorbed Ti displaces the surface Al, resulting in a mixed Ti/Al interfacial layer instead of a sharp Ti:Al2O3 interface. Our results provide a coherent picture of the structural and electronic properties of this interface and are consistent with available experimental data.