MOCVD ROUTES TO TL-2212 MGO/TL-2212 TRILAYERS - PRELIMINARY-OBSERVATIONS ON GROWTH AND MICROSTRUCTURAL/ELECTRICAL PROPERTIES/

The suitability of Tl2Ba2CaCu2O8 (Tl-2212) and MgO for growing SIS tri layers by metal-organic chemical vapor deposition (MOCVD) is examined. Low temperature (500 degrees C) epitaxial (100) MgO film growth on(11 0) LaAlO3 by MOCVD using Mg(dpm)(2) (dpm=2,2,6,6-tetramethyl-3,5-hepta nedionate) is demonstrated. Tl-2212 does not decompose under these MgO growth conditions, although decomposition occurs at lower O-2 partial pressures. To form trilayer structures, BaCaCuO(F) films are first gr own on (110) LaAlO3 by MOCVD using Ba(hfa)(2) . mep (hfa=1,1,1,5,5,5-h exafluoropentane-2,4-dionate: mep=2,5,8,11,14,17-hexaoxanonadecane), C a(hfa)(2) tet (tet=2,5,8,11,14-pentaoxapentadecane) and Cu(dpm)(2) pre cursors and are then post-annealed in the presence of bulk Tl2Ba2CaCu2 O8 to form Tl-2212. MgO is then deposited by MOCVD. Finally, a top TBC CO layer is grown by MOCVD and subsequent Tl2O anneal to complete the trilayer. Both of the TBCCO layers are highly oriented, while the MgO layers are largely polycrystalline due to the rough underlying Tl-2212 . Both TBCCO layers art: superconducting (T-c similar to 105 K).