Enhanced band structure, optoelectronic and magnetic properties of spray pyrolysis Ni-doped SnO2 nanostructured films

Pure and Nickel-doped Tin Oxide at 0, 1, 2, 4, 5, 6, and 7 wt % of Ni nanocrystalline thin films were synthesized by home-made Spray Pyrolysis technique on glass substrate. The microstructural, morphological, optical and magnetic properties of the films have been investigated. The XRD patterns of the films exhibit a tetragonal type structure with no signature of extra phases. The solubility limit of the incorporation of Ni into the SnO2 semiconducting matrix has been observed at x > 0.05. The nanocrystalline feature of the films is confirmed from AFM and SEM investigations. It was found that the optical energy gap E-g diminishes with the increasing of Ni content up to x <= 0.05 and then increases due to the solubility limit of Ni, suggesting the enhancement in the band structure. The decrease of the optical band gap could be attributed to the sp-d exchange interaction while the increase of E-g is explained according to the Burstein-Moss effect. The dispersion and single oscillator parameters of the films were estimated by analyzing the dispersion data based on Wemple-DiDomenico single-effective-oscillator model. The room temperature ferromagnetic behaviour of the films has been observed and discussed according to the bound magnetic polarons model.