Plasma optical emission studies of high- Tc superconducting and buffer thin film physical vapour deposition

Abstract

The non-intrusive technique of optical emission spectroscopy was used to identify the plasma species active in two different physical vapour deposition techniques: sputtering and laser ablation, when applied for high T c superconducting (HTSC) and buffer thin film deposition. Peak identification of the plasma optical emission spectra taken for targets of YBa 2Cu 3O 7 − x (YBCO), BiSrCaCu 2O 7 − x (BiSCCO 1112), Bi 2Sr 3Ca 3Cu 4O 7 −x( BiSCCO 2334), SrTiO 3, BaTiO 3, Y 2O 3-stabilized ZrO 2 (YSZ) and CeO 2 was made from published values and measured results for the constituting elements (Cu) and elemental oxides (Y 2O 3, BaCO 3, CuO). Aiming at determination of an appropriate criterion for in situ assessment of ambient oxygen sufficiency, the plasma optical emission was related to the deposited HTSC film characteristics. During YBCO RF single target off-axis sputtering and pulsed laser ablation the gas-phase preoxidation, witnessed by YO-optical emission, could be used as a qualitative criterion ensuring high quality film deposition. During dc magnetron sputtering with two-opposedtargets, the oxygen-to-argon peak actinometric ratio was used as a criterion instead. SEM investigation of the ablation-induced surface modification of targets of HTSC and buffer materials revealed specific topography for different target structure and density, which can influence the deposited film thickness uniformity. An extensive table is presented of the plasma emission lines and band heads for YBCO compiled from this work and that of other authors.