YBA2CU3O7-DELTA-THIN FILMS ON SAPPHIRE WITH BUFFER LAYERS OF CEO2

Epitaxial CeO2 buffer layers and YBa2Cu3O7-delta thin films have been grown in situ on (1102BAR) sapphire by electron beam evaporation. Buff er layers of only 20 nm thickness inhibit interdiffusion between YBa2C u3O7-delta and Al2O3 as determined by depth profiling using x-ray phot oelectron spectroscopy. The layers show smooth surfaces and narrow int erfaces. High lattice perfection of the CeO2 layer has been shown by x -ray diffraction. The first time Laue oscillations up to ninth order h ave been observed in thin CeO2 buffer layers. YBa2Cu3O7-delta films gr own on these buffer layers reveal T(c) = 88 +/- 0.5 K, rho(300 K) = 38 0 muOMEGAcm, and j(c)(77 K, 0T) = 1.3 x 10(6) A/cm2.