Aluminium-doped zinc oxide films prepared by an inorganic sol-gel route

Thin films of aluminium-doped zinc oxide have been formed on glass using an inorganic sol-gel route and the dip-coating process. The films were formed by the thermal decomposition of a stable precursor colloidal sol prepared by an ethanolic reflux of Zn(CH3COO)2·2H2O and Al(NO3)3·9H2O. Lactic acid was used as hydrolysis catalyst and acetylacetone and diethanolamine were added to improve film homogeneity. Thermal analysis was used to investigate the chemical processes during firing of the sols. Atomic force microscopy data revealed morphological changes in the temperature range 200-500 deg. C. The importance of sample firing after each transfer step was evidenced by the quartz crystal microbalance technique. A red shift of the absorption edge was observed for thicker films and the transmittance of the samples decreased with increasing film thickness