Preparation And Characterization Of ZnO Films By PLD

ZnO is a direct wide band gap compound semiconductor (E_g～3.37eV at 300K), it haslarge exciton binding energy about 60meV, theoretically, it can realize stimulated ultravioletemission at room temperature. ZnO can be applied in large area, for instance, transparencyelectrode, piezoresistance, cell battery, surface acoustic wave device, gas sensor andlight-emitting diode. So it is very important to prepare high quality ZnO thin film. Weprepared ZnO thin films by pulsed laser disposition (PLD), investigating the effect of mainparameters of experiment for preparing high quality ZnO thin films. Their properties werecharacterized by Reflection high energy electron diffraction (RHEED), X-ray diffraction(XRD), atomic force microscope (AFM), photo luminance (PL) spectra and hall effect. Theresults showed that for the ZnO thin films prepared on c-plane Al₂O₃, the crystal quality ofthe ZnO thin film enhanced with increasing the substrate temperature from 350℃to 550℃.When the substrate temperature further increased, the crystal quality of the thin filmdeteriorated. The sample prepared at 550℃exhibited the narrowest FWHM of (0002) peak,the clearest regular spotty RHEED image, good optical property (PL) and the highest Hallmobility. In another experiment, ZnO thin films were deposited on Si (111) at the temperatureof 650℃in oxygen under the pressure of 60 Pa by pulsed laser deposition (PLD) andannealed in air. The annealing temperature was from 500℃to 900℃. The growth time was370 min and the annealing time was 8 min. The results show that the sample annealed at600℃has the best crystal quality, and the surfaces of samples annealed at 500℃, 600℃and700℃are smoother than the surfaces of the as-grown sample and the samples annealed attemperature which are higher than 800℃. PL spectra shows that annealing in air make manydefects in ZnO thin films, so the ratio of UV demission about at 378nm to DL emissionbecomes small. It means that annealing ZnO thin film in air can enhance crystal quality butdoesn't have benefit to the VU emission.