Synthesis, characterization and thermal decomposition study of zinc propionate as a precursor for ZnO nano-powders and thin films

A simple, low-temperature and low cost water-based chemical solution method for the preparation of ZnO nano-powders and thin films is presented. A stable, clear and environmentally friendly precursor solution was obtained by the reaction of zinc acetate dihydrate, Zn(CH3COO)2·2H2O with an excess of propionic acid, CH3CH2COOH and the further addition of ammonia, NH3. The thermal decomposition process of the powdered solution was studied by TG/DTA analysis in air and in humid oxygen atmosphere coupled with a quadrupole mass spectrometer (QMS). The precursor solution was spin-coated on single-crystalline Si(1 1 1) substrates and thermally treated at 400 °C for 2 h in air in order to obtain ZnO thin films. The X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) investigations indicated that the synthesized ZnO nano-powders and thin films present a pure wurtzite structure. The morphology of the ZnO nano-powders and thin films was investigated by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), respectively. The photoluminescence spectra of the thermally treated powder and thin films present a maximum emission ultraviolet peak at 384 nm for the ZnO powder and at 379 nm for the thin films. The presence of the strong emission peak around 380 nm confirms a ZnO structure. The absence of emission in the 400–500 nm wavelength range states for the low content in defects and vacancies.