DIAMOND-LIKE CARBON-FILMS AS PROTECTIVE COATINGS FOR SUPERCONDUCTING YBA2CU3O7 FILMS

We have investigated the use of diamondlike carbon (DLC) films for protecting superconducting YBa2Cu3O7 (YBCO) films against degradation from exposure to moisture and acid. YBCO thin films on single crystal LaAlO3 and MgO substrates were deposited by laser ablation followed by DLC encapsulation. DLC films were deposited at pressures ranging from high vacuum to 0.1 Torr He. Substrate temperature was varied from 20 to 100-degrees-C during the deposition of DLC. The process compatibility of laser ablation was found convenient to sequentially deposit YBCO and DLC films from high purity stoichiometric targets. Epitaxial YBCO films on (100)LaAlO3 (T(c-zero)=89 K) and (100)MgO(T(c-zero)=85 K) 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.