Preparation of YBCO thin film by MOCVD method using new liquidmetal organic precursors

摘要

New low melting point yttrium, barium, and copper complexes were synthesized for metalorganic chemical vapor deposition (MOCVD), tris(2,2,6,6-tetramethyl-3,5-octandionato)yttrium (Y(TMOD)3), Ba(TMOD)2, and bis(6-ethyl-2,2-dimethyl-3,5-octanedionato)copper (Cu(EDMOD)2). The melting point of Y(TMOD)3, 95°C, is 80°C lower than that of the conventional tris(dipivalaylmethanato)yttrium (Y(DPM)3). The melting point of Cu(EDMOD)2 is 78°C, which is 120°C lower than that of Cu(DPM)2. For fabrication of YBa2Cu3Oy-δ thin films, these complexes were used in the liquid state where a stable deposition rate could be obtained; the Y(TMOD)3 and the Cu(EDMOD)2 were heated at 105°C and 90°C, respectively, and the mixture of Ba(DPM)2 and Ba(TIMOD)2 in the ratio of 4 to 1 was used at 215°C. Single crystal STO(100) was used as a substrate. Substrate temperature was 800°C. Thin films, of thickness 200 nm, were obtained. The XRD patterns of all the samples showed the preferred orientation of the c-axis normal to the substrate surface. The superconductivity was confirmed at 78 K