Pulsed laser deposition of ZnO nanocluster films by Cu-vapor laser

The dependence of stoichiometry, grain size, cathodoluminescence colors, adhesion, and surface morphology of zinc oxide films, deposited by a Cu-vapor laser at room temperature, as a function of oxygen ambient pressure during synthesis were investigated. Auger electron spectroscopy showed that ZnO films with a Zn/O ratio close to 1 were obtained at oxygen pressures >10−1 Torr. X-ray diffraction revealed that pulsed laser deposited zinc oxide films were composed mainly of nanocrystals, the average grain size of which grew from 5 to 17.5 nm as the oxygen pressure was increased from 10−5 to 1 Torr. The surface morphology of the films, as determined by secondary electron microscopy, also exhibited increasing roughness as the grain size increased. Films grown in an oxygen pressure >1.5×10−1 Torr glowed blue under electron bombardment, while slightly substoichiometric films glowed white under similar excitation. Films deposited in an oxygen background pressure up to 1.5×10−1 Torr exhibited good adhesion to substrates. Deposition rate on the order of 4.6 nm/s was obtained.