Fabrication and characterization of optical and electrical properties of Al-Ti Co-doped ZnO nano-structured thin film

Al and Ti Co-doped zinc oxide (ATZO) nano-structured thin films with 1 at % Al and 0.1 at % Ti were deposited on glass substrate via sol-gel technique. X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) methods were used to investigate the structure, morphology and surface roughness of the thin films. The optical properties were investigated by spectroscopic ellipsometry (SE) and UV-VIS spectrophotometer. The resistivity measurement was performed using a LCR-meter. XRD analysis confirmed the zinc oxide hexagonal wurtzite structure for the thin films. It was found that Ti doping reduces the roughness and grain size values to 8.2 nm and 50 nm, respectively. The optical band gap energy was concluded to be 3.23 eV for ZnO film and it increases to 3.26 eV for ATZO films. Refractive index decreased upon Ti doping as a consequence of increase in charge carrier concentration. All the thin films exhibit high transmittance over 85% in the visible wavelength region. Ti replacement causes to decrease in resistivity and minimum resistivity value of 13 × 106 Ωcm was measured for ATZO thin film.