Low-resistance contacts on YBa2Cu3O7−δ ceramics prepared by direct wire bonding methods

Wire bonding, such as electric discharge spot welding and ultrasonic bonding, has been investigated for use in simple, conventional methods of preparing low-resistance ohmic contacts on superconducting Y1 Ba2 Cu3 O7−δ ceramics. Spot welding with thermal annealing improves the contact’s resistivity to 2×10−7 Ω cm2 , while a sample without annealing shows non-ohmic and semiconductive characteristics. Change in the crystal structure induced by high current is analyzed. Ultrasonic bonding with annealing at 500 °C achieves 3×10−8 Ω cm2 , one of the lowest contact resistivities ever obtained in simple methods. The current-voltage characteristics show nonlinearity, which is attributed to the superconducting state of the Ag/Y1Ba2Cu3O7−δ interface.