ZnO thin films prepared by a modified water-based Pechini method

ZnO films were prepared by a modified water-based Pechini method where ethanol was added to avoid some disadvantages of solely water-based precursor solution. The ratio of ethanol to water (E/W) largely influences the quality of films, and the appropriate ratio is about 1.2. FT-IR spectra show that the addition of ethanol largely promotes the esterification reaction in the dried gel. XRD results show that all films are of wurtzite structure while the annealing temperature is not higher than 700 °C. The secondary phase Zn2SiO4 was found in the films annealed at 800 °C because of the reaction between SiO2 substrate and ZnO film. SEM photographs show that all films consist of nanocrystalline grains with sizes in the range of 25–82 nm, and the addition of ethanol improves the growth of grains. Transmittance spectra reveal that all films have high average transmittance of about 90% in the range of 450–800 nm except those annealed at 800 °C. The average optical band gap of films is about 3.29 eV.