In Situ Epitaxial Growth Of Y₁Ba₂Cu₃O_7-δ Films By Magnetron Sputtering

Y1Ba2Cu3O7-δ(YBCO) is the material of high-temperature superconductor that enters its track of applications. YBCO film has been continuous hot pot in the community of related researches. La0.5Ba0.5CoO3(LBCO) is Co-based perovskite structure materials with new functions. LBCO has ferromagnetic property and giant magneto resistance effect at low temperature (100-150K). The structure of LBCO/YBCO film is expected having a promising future in making ferromagnetic/superconductive heterojunction, which will provide a wide range of potential applications in data storage, medical instrument and the other devices.Using the reactive radio-frequency magnetron sputtering method, epitaxial Y1Ba2Cu3O7-δ (YBCO) thin films were in-situ deposited on the (100) MgO substrates. The YBCO films were studied with the structural and morphological characterization using X-ray diffraction (XRD) and atomic force microscopy (AFM). We changed the conditions of film growth such as sputtering power, sputtering pressure and use La0.5Ba0.5sCoO3(LBCO) film as the buffer layer. The on-aixs magnetron sputtering device was used to produce the c-axis single crystal epitaxial YBCO thin films under the combinations of different power and pressures. The results are summarized as follows:1. Study of deposition technology related to the parameters of sputtering power, pressure, temperature, and the ratio of O2/Ar etc. YBCO films are found to be possible with the ratio O2/Ar of20:1at the temperatures higher than700℃. At the temperature of800℃, the matched combination of input power and work pressure are decisive for the growth of c-axis YBCO films. The c-axis epitaxial YBCO thin films can be obtained either under the high power/the high pressure or under the low power/the low pressure though they are not fully cube-on-cube growth of single crystals. AFM measurement shows that the directly epitaxial growth on MgO substrate gives rise to a rather rough surface of YBCO films.2. The LBCO buffer layer is used to improve the crystallinity of the YBCO film. The XRD patterns of φ-scan mode show that the YBCO films with LBCO buffer layer are4-fold in symmetry, evidencing that they are fully cube-on-cube growth of single crystals. The use of LBCO buffer layer enhances the XRD intensity of (003) and reduces its full width at half maximum. The values of FWHM in the rocking curves are decreased from1.9°to0.83°.3. Using the LBCO film as the buffer layer, the roughness of the films is significantly reduced from10.5nm to around1.8nm in the measure of the Root-Mean-Square (RMS) roughness, being helpful for fabrication of devices in applications. In addition, the size of grains is found to decrease after the LBCO film is used as the buffer layer.