Superconducting YBa2Cu3Ox Films Research Articles

Effects of plasma enhancement on the carrier-gas-free metalorganic chemical-vapor deposition of oxide superconducting thin films

The effect of plasma enhancement on carrier-gas-free metalorganic chemical vapor deposition of superconducting YBa2Cu3Ox films has been investigated based on crystallographic studies, plasma diagnosis, and composition analysis of the gas phase. With plasma enhancement, the oxygen pressure needed for growing thin films with YBa2Cu3Ox structure is reduced from 4.0×10−2 to 2.0×10−2 Pa. YBa2Cu3Ox films grown with plasma-enhancement at oxygen pressure of 4.0×10−2 Pa showed zero resistivity at 86 K and a critical current density of 2×105 A/cm2 at 77 K. Plasma enhancement also was found to increase oxidizing activity by three orders of magnitude during the cooling process. Plasma diagnosis indicated that superconducting properties of grown films are related to plasma density, which can in turn be related to the concentration of active oxygen. Composition analysis of the gas phase indicated that plasma enhancement increases reaction between oxygen and metalorganic sources or their derivatives. The effect of plasma enhancement on oxidizing activity clearly differs between growth and the cooling process, and this difference may be due to the consumption of activated oxygen by metalorganic sources or their derivatives.

Superconducting YBa2Cu3Ox films prepared by rf plasma flash evaporation

Superconducting YBa2Cu3Ox films were prepared by rf plasma flash evaporation on MgO(100) single crystals. 4 MHz rf Ar–O2 plasma was used and Y–Ba–Cu–O (YBCO) powder as raw material was fed into the plasma. The growth rate of 730 nm/min was achieved. Texture of the grown films varied from a-axis orientation to c-axis with increasing growth temperature and decreasing growth rate. The films without heat treatment exhibited zero resistance temperature (Tc0) more than 77 K. The deposited films using the stoichiometric powder were slightly poor in Y. The sample using Y-rich powder revealed nearly stoichiometric composition and exhibited a Tc0 of 90.6 K and a critical current density (Jc) of 6.8 × 105 A/cm2 at 77 K in zero applied field.

Ion beam analysis of oxygen distribution in superconducting YBa2Cu3Ox

It has been shown that by combining the elastic scattering of protons and Rutherford scattering of α particles, the total composition and oxygen distribution of superconducting YBa2Cu3Ox films and bulk samples can be analyzed. The non-Rutherford scattering due to the 16O(p,p0)16O reaction enhances at the bombarding energy of 2.3 MeV the elastic scattering cross section by a factor of 5 over the cross section of the Rutherford scattering and makes it possible to determine the oxygen distribution in the matrix of heavy elements Y, Ba, and Cu.