Evaluation of low resistance contacts on YBa₂Cu₃O₇ thin films using the transmission line model

In measurements of low contact resistances in planar geometries, the current density through the contact can be inhomogeneous. If this inhomogeneity is neglected, serious systematic errors can occur when calculating the specific contact resistivity. In this work, the transmission line model, commonly used in semiconductor technology, is applied to account for the inhomogeneous current density in low ohmic contacts between gold or silver and YBa₂Cu₃O₇ thin films. To evaluate the influence of preparation parameters, several fabrication techniques and different kinds of YBa₂Cu₃O₇ thin films have been used to form the metal-YBa₂Cu₃O₇ interface. Contact resistivities as low as 1*10^-9 Omega cm² have been obtained.