Temperature-dependent composition of Fe/TiO2(1Â 1Â 0) and Fe/TiO2(0Â 0Â 1) interfaces

The Fe thin films where deposited on rutile TiO2(1 1 0) and (0 0 1) substrates prepared in different ways involving Ar+ bombardment and annealing in ultra-high vacuum. It is shown that apart from the crystallographic orientation of the substrate the type of preparation method generating different amount and distribution of Ti interstitials affects the diffusion of Fe into the bulk TiO2 especially at lower temperatures (up to ∼800 K). The amount of surface Fe can be decreased to the level of a few atomic percent for annealing at 1000 K on both types of substrates. However, in the case of TiO2(0 0 1) the considerable amount can be restored by additional annealing at medium temperatures (∼673 K) and it is not observed for TiO2(1 1 0). The effect although not fully understood can be repeated many times without loosing its intensity.