ANISOTROPY ON THE A, B-PLANE OF C-AXIS ORIENTATED ALMOST TWIN-FREE YBCO FILMS ON NDGAO3

Thin YBCO films have been grown epitaxially on twin-free (001) NdGaO3 substrates with off-axis DC magnetron sputtering at right angle from a stoichiometric target. The films are 200 nm thick and have c-axis orientation. A very small amount of a-axis orientated grains has been achieved. According to diffractometric measurements the a-axis of the major part of the YBCO film has only one common direction in the plane of the substrate. The critical temperature for zero DC resistance is T(co) = 88 K. The expected anisotropy of the specific resistances in the a, b-plane has been demonstrated with DC measurements. The ratio of the specific resistances in a- and b-direction is almost temperature independent between 110 K and room temperature. Ratios up to rho(a)/rho(b) = 2.1 have been achieved. At 100 K the specific resistance in the direction of the b-axis is rho(b) almost-equal-to 50-mu-OMEGA cm for a ratio rho(a)/rho(b) = 2.