High optimization of crystallization experimental conditions of ZnO nano thin films prepared by spray pyrolysis technique for optoelectronic applications

The present study intends to provide the impact of nitric acid on the structural and optical characteristics of thin films of ZnO. The latter was grown on substrates of glass via spray pyrolysis with 400°C, using Zinc acetate aqueous solution acidified by different amounts of nitric acid to obtain a pH ranging from 6.8 to 2.9. The film properties were analyzed as a function of pH. In the light of the XRD analysis, all the films have a preferential direction along the (002) plane. Depending on pH conditions, the crystal size increased from 32.38 to 37.4 nm, with a decrease in pH from 6.8 to 2.9, according to the X-ray diffraction analysis. It can be observed from the transmission spectra of the 300-900 nm wavelengths range that the optical transmission of the films is on average above 90%, and band gap values were found in the range 3.28 - 3.19 eV. The ZnO film’s FTIR spectrum in the wavenumber range (400-4000 cm-1) displayed a wide band between 400 and 552 cm-1, which was assigned to the Zn-O stretching mode.