Time and thickness dependence of crystallization of amorphous magnetron deposited TiO2 thin films

Titanium dioxide films have many remarkable properties, for example photocatalytic activity and hydrophilicity. However, these properties depend significantly on the crystallinity, phase composition and microstructure of the films. In this study, crystallization of amorphous films with different thickness (50-2000 nm) deposited on silicon substrates was investigated by XRD in-situ isochronal and isothermal annealing at different temperatures and compared with the post-annealing of both amorphous and nanocrystalline films. It was found that the crystallization depends strongly on the film thickness, especially below about 500 nm and it is slow for very thin films. The process can be well described by the Avrami equation modified by the initial time of crystallization. The parameters of the equation depend on the film thickness.