Reflectometry and small-angle X-ray scattering on thin films produced via sol-gel route

Reflectometry, diffraction and grazing incidence small angle X-ray scattering have been used to characterize zirconia (ZrO2) thin films obtained by the sol-gel route, during low temperature treatment. Different microstructural parameters of the films such as thickness, density; phase, grain size and spatial arrangement, have been determined. Thin films were formed on mirror-polished sapphire (Al2O3) wafers by a dip-coating process in a zirconia precursor sol. Before thermal treatment, the layer is amorphous and the thickness is about 140 nm. After thermal treatment at 600 degreesC during 30 minutes, the layer thickness decreases to 60 nm while the density increases. After crystallisation in the zirconia tetragonal form, the coating is made of randomly oriented nanocrystals. This structural evolution is similar to that of a conventional xerogel showing that the interface does not modify the microstructure of the layer. The nanocrystalline layer results in a relatively dense thin film.