Influences of Substrate and Annealing on the Structural and Optical Properties and Photoluminescence of Nanocrystalline ZnO Films Prepared by Plasma Assisted Pulsed Laser Deposition

Single-crystalline silicon, amorphous quartz, and single-crystalline sapphire were used as the substrates for the deposition of nanocrystalline zinc oxide (nc-ZnO) thin films by plasma assisted pulsed laser deposition from metallic zinc at low temperature below 80 °C, and a postdeposition annealing process was performed for the deposited nc-ZnO thin films. The influences of substrate and annealing on the structural and optical properties as well as the photoluminescence of the prepared nc-ZnO thin films were studied. Raman spectroscopy and Fourier-transform infrared spectroscopy measurements reveal the wurtzite ZnO phase in the films. X-ray diffraction results indicate the nanocrystalline structure of the films with c axis perpendicular to substrates. Optical characterization shows that the prepared films have an ultraviolet (UV) absorption edge near 380 nm with a direct band gap of about 3.25 eV. The prepared films emit predominantly UV photoluminescence at light excitation. The structure and properties of the films are dependent on substrates and the annealing process has different influences for the films deposited on different substrates.