Gas-phase oxidation chemistry during pulsed laser deposition of YBa ₂Cu₃O_7-δ films

The gas-phase processes relevant for oxidation during growth of YBa 2Cu3O7-δ (YBCO) films by pulsed laser deposition in different oxidizing ambients are discussed using a phenomenological model. The model consists of an accounting for the neutral species generated from the target during laser ablation, and their attenuation due to reactive and elastic scattering during transport, to determine the flux of neutral cation and anion species incident onto the substrate. In particular, the oxygen (O and O2), cation (Y, Ba, and Cu), and diatomic oxide fluxes in the presence of O2, O3, N2O, or NO2 as background oxidizer gases are qualitatively analyzed based on the known photochemical and electron-impact dissociation, and oxidation reactions of these gases. The relative effectiveness of these oxidizing agents, as judged from their propensity to produce diatomic oxides and atomic oxygen in the gas phase, is found to be in qualitative agreement with the previously observed trends in their oxidation behavior as deduced from the superconducting characteristics of YBCO films prepared using these gases.