EPITAXIAL Y1BA2CU3O7-DELTA THIN-FILMS WITH (103) (110)-ORIENTATION AND (100)/(010)-ORIENTATION ON NDGAO3 AND SRTIO3 SUBSTRATES GROWN BY ION-BEAM SPUTTER-DEPOSITION/

A fully oxygen-compatible ion-beam sputter deposition process (IBS) ha s been implemented for investigation of four film/substrate couples: ( 103)/(110) YBCO on (110)SrTiO3 (STO) and on (100)NdGaO3 (NGO), and (10 0)/(010)YBCO on (110)NGO and on (100)STO. For comparison, some (103)/( 110)YBCO films have also been prepared by off-axis rf-magnetron sputte ring. Below about 600-degrees-C semiconducting, sub-nm flat, and perfe ctly single-crystalline YBCO films crystallize on these substrates wit h a crystallographic unit cell of about 1/3 of the Cu-O subcell of YBC O and perfect registration with the Ti4+ -O and Ga3+ -O sublattice of STO and NGO, respectively. At higher temperature superconducting YBCO films grow coherently epitaxially in the first approximately 100 nm th ickness; in thicker films the lattice-misfit strain relaxes to the ''f ree'' lattice constants. Above approximately 680-degrees-C a faceted ( 103)YBCO orientation grows on (110)STO and (100)NGO substrates with un iform in-plane orientation of the [010]YBCO direction parallel to [001 ]STO and [001]NGO. Along [010]YBCO the (103)YBCO films exhibit high cr ystalline perfection and intrinsic superconducting properties approach ing those of (001)YBCO films in the plane; i.e., T(c,0) > 88 K, DELTAT (c,0) < 0.6 K, R300/R100 > 2.9, rho100 > 250 muOMEGAcm, and j(c) (77 K ) greater-than-or-equal-to 10(6) A/cm2. Practical use of (103)YBCO fil ms is hampered by the large surface roughness. Above approximately 680 -degrees-C a mixed (100)/(010)YBCO orientation grows on (110)NGO subst rates, exhibiting a very smooth surface but less attractive supercondu cting properties; typically, T(c,0) less-than-or-equal-to 80 K, DELTAT (c,0) approximately 1 K, R300/R100 approximately 1.2, rho100 > 3 mOMEG Acm, and j(c) (77 K) less-than-or-equal-to 10(5) A/cm2. On (100)STO su bstrates the YBCO film orientation varies from pure (100)YBCO between approximately 580 and approximately 630-degrees-C and mixed (100)/(010 )YBCO below approximately 660-degrees-C to pure (001) YBCO above appro ximately 670-degrees-C. With rising temperature the surface roughness increases from <2 to approximately 6 nm-rms, while the other parameter s continuously improve to state-of-the-art values for c perpendicular- to-oriented films. Specifically, mixed (100)/(010)YBCO films reach T(c ,0) > 86 K, DELTAT(c,0) approximately 1 K, R300/R100 > 2.8, rho100 < 3 mOMEGAcm, and j(c) (77 K) > 10(5) A/cm2. (100)/(010)YBCO films on (10 0)STO are a promising candidate for sandwich-type SIS-JJ.