Abstract
By using the off-axis RF magnetron sputtering method, we have fabricated YBCO thin films on YSZ [100] substrates with two distinct in-plane orientations, namely, YBCO [100] // YSZ [100] (0^0 in-plane orientation) at 825^0C and YBCO [110] // YSZ [100] (45^0 in-plane orientation) at 670^0C. Both thin films have critical temperatures T_{C0} in the range of 86~88K and critical current densities at 5K in the range of 9 X 10^6 A/cm^2 ~ 1.2 X 10^7 A/cm^2. To fabricate the 45^0 grain boundary junctions, we first deposit a thin YBCO [100] film at 825^0C on the substrate and remove part of the film by ion-milling. Then a thicker YBCO film is deposited at 670^0C. We show that the filmdeposited on the ion-bombarded substrate can maintain its 45^0 in-plane orientation while the film deposited on the YBCO [100] film keeps the 0^0 in-plane orientation. The critical currents densities of our 45^0 grain boundary are in the range of 10^3~10^4 A/cm^2 at 5K and the modulation curves are anomalous Fraunhofer patterns because of the inhomogeneous critical current densities result from the faceting effect and the d_{x^2-y^2} symmetry of the order parameter.