High critical temperature grain boundary Josephson junctions

Josephson junctions of the grain boundary type (bicrystal, step-edge) were studied from the point of view of de and rf properties. Temperature and magnetic field dependences of the critical current density are strongly affected by the YBa2Cu3O7-x, thin film morphology and tunneling current homogeneity, and high frequency properties by the order parameter depression at the boundary interface. In the case of bicrystal junctions the measured de and rf characteristics follow ideally the dependences calculated using the RSJ model with finite capacitance. The step-edge junctions had suffered under interface inhomogeneities and grain boudary defects, strongly degrading the weak link properties.