Structural and optical characterization of nitrogen and gallium co-doped ZnO thin films, deposited by sol-gel method

Abstract

Nitrogen and gallium co-doped ZnO films have been successfully obtained by a sol-gel technology using spin coating. ZnO:N, ZnO:Ga and co-doped (N, Ga) ZnO films are deposited on silicon and quartz substrates. The structural, morphological and optical properties of ZnO:N:Ga thin films are studied depending on the thermal treatments (300–600 °C) and the two dopants: N and Ga. The investigations of the doped ZnO films have been performed by using X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Field Emission Scanning Electron microscope (FESEM) and UV–VIS–NIR spectrophotometry. It has been found that the co-doped (N, Ga) ZnO films are crystallized in the wurtzite structure with no impurity phases. The optical transparency of ZnO:Ga and ZnO:N:Ga films is above 80% in the spectral range of 400–800 nm, revealing a significant improvement compared to undoped ZnO films. Gallium and nitrogen co-doping in ZnO results in the modification of the surface morphologies changing from wrinkle-like (undoped ZnO) to closed packed grained microstructure (ZnO:N:Ga films).