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

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Abstract
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.