Microstructure and optical properties of sol-gel zirconia films

Films of zirconia, 40 to 140 nm in thickness were deposited on sapphire (1120) single crystals by dip coating from a zirconium n-propoxide sol. Thickness was varied by repeatedly coating the substrate with intermediate drying at 50degC. The as deposited films were amorphous and changed to cubic and monoclinic phases after heating to 450degC and 900degC respectively. Monoclinic film had a strong (002) texture. Heating of the thinner films to 1250degC results in development of porosity in the film and in grain growth. Porosity develops because of a relatively high contact angle between the saphire and zirconia. The optical band gap energy of the film is found to be 5.50 eV. (author). 14 refs., 2 tabs., 5 figs