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

We have investigated the use of diamondlike carbon (DLC) films for pro tecting superconducting YBa2Cu3O7 (YBCO) films against degradation fro m exposure to moisture and acid. YBCO thin films on single crystal LaA lO3 and MgO substrates were deposited by laser ablation followed by DL C encapsulation. DLC films were deposited at pressures ranging from hi gh 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 an d DLC films from high purity stoichiometric targets. Epitaxial YBCO fi lms on (100)LaAlO3 (T(c-zero)=89 K) and (100)MgO(T(c-zero)=85 K) subst rates showed identical superconducting transitions before and after en capsulation by a DLC layer. The encapsulated films showed no degradati on due to acid treatment or aging over a period of 45 days.