Optical absorption spectroscopic diagnostics during sputter deposition of Y-Ba-Cu-oxide

Optical absorption spectroscopy has been used in situ as a diagnostic for studying the sputter deposition of high-temperature superconductors. Both atomic and molecular species were monitored using hollow-cathode lamps as line sources and a quartz tungsten-halogen lamp as a broadband source. Measurements were made of the relative atomic and molecular species concentrations in front of the target during sputtering of Y-Ba-Cu-oxide targets using a Kaufman ion gun. The absorption measurements showed that the fluxes of ground state Ba, Cu, BaO, and CuO ejected from a composite target during argon- and oxygen-ion bombardment varied greatly with sputtering parameters. Absorptions due to Y and YO were too weak to be reliably measured. Various studies of the effects of changes in ion-beam energy, ion flux to the target, target temperature, oxygen content of the beam, and incident ion angle were performed. Stoichiometry of deposited films was also measured and correlated to the absorption results. Absorption measurements during argon- and oxygen-ion sputtering of a pure copper target were made for comparison with the results from the superconducting target. These measurements show that the relative density of species ejected from the target is highly dependent on the sputtering conditions, and indicate that careful control of beam parameters is essential for repeatable stoichiometry in deposited films.