Articles you may be interested inPreparation of baxis oriented YBa2Cu3O y thin film by laser metalorganic chemical vapor deposition and successive annealing

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Recently we have found a very effective method for controlling the orientation of YBCO films by metal-organic chemical vapor deposition (MOCVD) using uv laser irradiation during deposition onto a MgO(lOO) substrate. The irradiated part was strongly a-axis-oriented normal to the surface of the substrate for films prepared at 650-700 °C, whereas the unirradiated parts showed c-axis or (110) orientation. This phenomenon occurs not only on MgO(100) substrates but also on other substrates. We obtained a Tc above 81 K on the a-axis oriented part. The critical current density was over 105 A/cm2 at 4.2 K and 0 T. The surface morphology depends on the laser power density and the repetition rate. A high degree of the a-axis orientation is obtained only by using uv light during deposition of YBCO film. IR or a visible laser causes only surface melting and the destruction of film orientation. We propose that the nuclei for a-axis orientation are formed by the aggregation of Ba caused by uv laser irradiation near the film surface.

YBa2Cu3O7-δ films containing an excess amount of Cu were prepared on MgO(001) at 650-750°C by chemical vapor deposition using β-diketone metal chelates. In the films prepared at the low temperatures of 650°C and 700°C, the degree of c-axis orientation was enhanced with increase of the Cu content from Y:Ba:Cu=1:2:3 to 1:2:4, and the films with Cu-rich content showed higher T c values than the films close to the stoichiometric composition. At the higher temperature of 750°C, a supplied excess of the Cu element affected the in-plane alignment of the grains and critical current density.

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