INVESTIGATION OF LASER-INDUCED PLASMA EMISSION FOR ZnO THIN FILM DEPOSITION

Abstract

ZnO plasma emission was investigated by ICCD camera fast imaging and by time integrated optical emission spectroscopy into vacuum and oxygen ambience. The ZnO plasma was induced by a KrF excimer laser ablation of zinc oxide target. This experiment was carried out at different O2 pressures from 10-2 to 10 mbar. Based on experimental findings by fast imaging, plume expansion as a function of ambient gas can be categorized into three different regimes, low (< 10-2 mbar), intermediate (10-2 < P < 1 mbar) and high pressures (> 1 mbar). Each of these regimes is characterized by a particular behavior of plume dynamics; freely expansion, plume splitting and enhancement of intensity and hydrodynamic instability and shock-wave-like propagation of the plume. The time integrated optical emission spectra acquired at a certain distance from the target into vacuum and for 0.1, 1 and 5 mbar oxygen pressures reveals several emission lines due to neutral zinc Zn*, zinc cation Zn+* and oxygen atom O* but no feature attributable to excited oxygen cations were identified. By comparing time integrated optical spectrum of plasma taken at different distances, the emission intensity of Zn+* line decreases as the distance from the target increases and disappears far from it. Furthermore, ZnO thin films were deposited in the three different regimes of O2 pressures used in order to correlate between plasma dynamics and deposited film characteristics.