Structural, optical, and morphological properties of laser ablated ZnO doped Ta2O5 films

ZnO doped tantalum oxide films (doping concentration 0, 1, 3 and 5 wt.%) have been prepared by pulsed laser deposition technique in reactive oxygen atmosphere and the films are annealed at temperatures 973 and 1173 K. The films are characterized using grazing incidence X-ray diffraction (GIXRD), micro-Raman and Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and UV–visible spectroscopy. XRD analysis shows that the ZnO doped films annealed at 973 K are crystalline in nature, whereas, the annealed counterpart of pure Ta2O5 is amorphous. On annealing at 1173 K, the undoped film shows good crystallinity, whereas, the ZnO doped film presents a decline in crystallinity compared to that of the films annealed at 973 K. The lattice constants, particle size and biaxial strains of the films are calculated from the XRD data. FTIR and micro-Raman measurements confirm the presence of Ta–O, Ta–O–Ta and O–Ta–O bands in the films. Ta2O5 nanorings of diameter around 700 nm have been observed in the AFM micrographs of 3 and 5 wt.% ZnO doped Ta2O5 films. Optical parameters like transmittance, reflectance, band gap energy, refractive index, and extinction coefficient of the films are calculated and are found to vary with ZnO doping.