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Published online by Cambridge University Press: 01 January 1992
We have investigated the deposition and superconducting properties of YBCO thin films on single crystal LaAlO3, MgO and polycrystalline alumina substrates followed by the DLC (diamond like carbon) encapsulation [1]. DLC films were deposited at pressures ranging from high vacuum to 100 mT He. Substrate temperature was varied from 21°C to greater than 100°C. The process compatibility of Laser ablation technique for depositing both the materials was found convenient to sequentially depositYBCO and DLC films from high purity stoichiometric targets. Epitaxial YBCO films on (100) LaAlO3, (Tc−zero = 89K) and (100) MgO (Tc−zero = 85K) substrates showed identical superconducting transitions before and after encapsulation by a DLC layer. The encapsulated films showed no degradation due to acid treatment or aging over a period of 45 days. Similar results were obtained for YBCO films on polycrystallinealumina substrate. A buffer layer of YSZ was essential to obtain good superconductingproperties on alumina substrate. A 200 nm thick YSZ provided the barrier necessary for minimizing the interface reaction between Al2O3 and YBCO. Typically a Tce = 86 K was obtained for these films. These films were textured with c-axis perpendicular to the substrate surface. Likewise, there was no degradation of superconducting properties of these films after deposition of the DLC films or chemical attack by dilute HNO3.