Xin Di Wu

Growth of high-Tc superconducting thin films for microwave applications

High Tc superconducting thin films of YBa2Cu3O7-(delta ) (YBCO) were deposited on sapphire substrates with buffer layers of yttria-stabilized zirconia and cerium oxide by using pulsed laser deposition (PLD) technique. The epitaxial relationship between the substrate and buffer layers as well as the buffer layer and the superconducting film was established. Furthermore, using the same thin film technique, YBCO superconducting thin films were deposited on both sides of substrates of up to 5 cm in diameter. The superconducting properties of the films on both the sapphire with buffer layers and large-area substrates were comparable to the ones of the best YBCO films.

Plume dynamics of excimer-laser-vaporized YBa2Cu3O7-delta material

Pulsed laser deposition of thin films is a technology that has been explored in some detail. Because of the difficulty of monitoring in real time either the ablation process itself, or thin film growth, many studies have relied on diagnostics of either the ablated plume (emission, absorption, fluorescence) or the resulting films (Tc, Jc, X-ray, RBS) to infer information about the overall process. This indirect approach has provided some vital information for improving the production of high-temperature superconductors. In this study the plume dynamics during the in-situ pulsed laser deposition of YBa2Cu3O7-(delta ) thin films are investigated. The 248 and 308 nm lines of an excimer laser were used to generate a plume from a bulk YBa2Cu3O7-(delta ) target. Variations in the plume distribution as a function of processing gas, pressure, fluence, energy, and spot size were monitored by resulting film distribution and composition and time resolved emission imaging. Results indicate that the plume distribution can be controlled to some extent by the incident laser beam size; in addition, broadening increases with increasing oxygen pressure.

Pulsed-laser deposition of YBa2Cu3O7-x thin films: processing, properties, and performance

One and two inch diameter wafers of (100) LaAlO3 have been coated with thin films of YBa2Cu3O7_ by a pulsed laser deposition technique. Deposition parameters have been optimized to produce uniform, 90 K films which have surface resistance values between 0.4 and 0.8 mμ at 4 K and 22 GHz.