Highly transparent and conducting Al-doped ZnO as a promising material for optoelectronic applications

Al-doped ZnO (AZO) thin films have been deposited onto the glass substrate via sol-gel spin coating method with different Al concentrations (0, 2, 4, 6, 8, 10 at.%). The growth orientation and crystalline structure were investigated by studying the X-ray diffraction (XRD) pattern. The XRD results reveal that the thin films show wurtzite phase with preferential orientation along the c-axis (002) plane for lower concentration of Al. The diffraction peak gets weaker corresponding to plane (002) and the diffraction peaks of planes (101) and (100) become stronger with higher concentration of Al content. The field emission scanning electron microscopy (FE-SEM) images confirm that thin films show wrinkle-type structure with a few minor cracks. The transmittance spectra of thin films were recorded by UV-Vis spectrophotometer in the wavelength range 350-800 nm. The optical transmittance of thin films was found to be above 85%. The band-gap energy of AZO films varies from 3.16 eV to 3.27 eV with increasing concentration of Al. The better conductivity and high optical transparency of AZO films make them a more promising alternative to indium-doped tin oxide (ITO) for optoelectronic applications.