Abstract
Al-doped zinc oxide thin films with 2 at.% were grown on silicon substrates at various substrate temperatures (200-500 degrees C). The Al-doped zinc oxide films were grown by the pulsed laser deposition method at constant oxygen pressure. The pulsed laser deposition target used was an Al-doped zinc oxide 2 at.% nanopowder synthesized by the modified sol-gel process. The microstructural, optical, and textural properties of Al-doped zinc oxide thin films were studied. From the X-ray diffraction measurements, the orientation of Al-doped zinc oxide films was found to be a c-axis, displaying only a (002) diffraction peak. X-ray diffraction spectra revealed that crystalline quality of the films enhanced, and grains became bigger with increasing the substrate temperature. Atomic force microscopy images show the formation of columnar grain in the thin Al-doped zinc oxide films with low surface roughness when the substrate temperature increases. By using the Tauc-Lorentz model, the optical constants of Al-doped zinc oxide films were deduced from spectroscopic ellipsometry data in the 1-6 eV photon energy range. spectroscopic ellipsometry results revealed that optical constants of the Al-doped zinc oxide films are strongly dependent on substrate temperature. The Al doping in ZnO and its growth on Si substrate introduce a tensile stress in the films which depends on the substrate temperature.