Microstructural study of SnO₂ thin layers deposited on sapphire by sol-gel dip-coating

Tin oxide (SnO₂) films have been grown onto (006) sapphire substrates by sol-gel dip-coating using tin alkoxide solutions. It is shown, using grazing-incidence X-ray diffraction, reciprocal space mapping and atomic force microscopy, that thermal annealing at 500 °C induces the crystallization of SnO₂ in the rutile-type phase. Further annealing treatments at temperatures lower than 1100 °C give rise to slow grain growth controlled by surface diffusion, whereas rapid grain growth (controlled by an evaporation-condensation mechanism) takes place at temperatures higher than 1100 °C. Concomitantly, the film splits into isolated islands and a fibre texture occurs at higher temperatures.