Gas-phase oxidation of copper during laser ablation of YBa 2Cu3O7-δ in different oxidizing ambients
Abstract
The gas-phase production of CuO during ablation of a YBa2Cu 3O7-δ target in the presence of three different oxidizer background gases: oxygen (O2), nitrous oxide (N 2O), and nitrogen dioxide (NO2), has been monitored using laser-induced fluorescence. The oxides of nitrogen are found to be much more efficient than oxygen in the production of CuO, with the order of reactivity being O2<N2O<NO2. In general for all the reactant gases, and independent of the ablation laser wavelength (193 and 308 nm), the CuO concentration has been observed to initially increase with increasing background gas pressure to reach a maximum before decreasing again to negligible levels at higher pressures. The rate of increase in the CuO concentration and its subsequent decrease with pressure, while being dependent on the nature of the oxidizer gas, is also very sensitive to the laser fluence used for ablation. The results are discussed in terms of the reaction energetics and the known dynamics of other gas-phase metal oxidation reactions.