Aluminium doped zinc oxide films: formation process and optical properties

Aluminium doped zinc oxide films were prepared through a non-alcoxide sol-g el and dip-coating technique, from zinc acetate and aluminium nitrate in et hanolic solution. The acetate hydrolysis was promoted by lactic acid. The d oping level of aluminium was 0.8 mol%. Acetylacetone and diethanolamine wer e used as additives to improve him homogeneity. The chemical processes whic h occur during the drying and oxide formation were followed by thermogravim etric and differential thermal analysis, using zinc acetate analysis for co mparison. An endothermic peak at about 350 degrees C and an exothermic peak at 460 degrees C for the dried solution used in the film preparation diffe r considerably from the peaks in the data for pure zinc acetate. The zinc o xide formation was confirmed by the diffraction peaks at 2 theta angles bet ween 30 degrees and 40 degrees, as well as by the luminescence spectra of t he films both in ultraviolet and visible regions. The optical band gap show s a dependence on additives with acetyacetone showing a larger effect. (C) 1999 Elsevier Science B.V. All rights reserved.