In-situ X-ray diffraction studies of time and thickness dependence of crystallization of amorphous TiO2 thin films and stress evolution
Abstract
Remarkable properties of titanium dioxide films such as hydrophilicity or photocatalytic activity depend largely on their phase composition, microstructure and in particular on the crystallinity. By in-situ X-ray diffraction studies of isochronal and isothermal annealing of amorphous films with different thickness at different temperatures it was found that the crystallization process can be quite well described by the Johnson-Mehl-Avrami-Kolmogorov formula modified by the introduction of crystallization onset.
This and other parameters of the formula strongly depend on the film thickness. For thickness below about 500 nm the crystallization is very slow.
Simultaneously, the appearance and increase of tensile stresses with the annealing time were observed. The tensile stresses generated during the crystallization rapidly increase with decreasing thickness of the films and inhibit further crystallization, and cause significant thickness dependence of the crystallization.