Abstract

There is a tremendous interest in high T_c superconducting thin films of Y₁Ba₂Cu₃O_7–x for device applications. However, most of the superconducting film fabrication techniques reported so far consist of a postannealing step in oxygen at temperatures around 850°C.¹ Degradation of the film surface and enhanced interfacial diffusion are major drawbacks in these techniques. We have developed a plasma-assisted laser evaporation technique that enables us to produce as-deposited superconducting Y₁Ba₂Cu₃O_7–x thin films at processing temperatures lower than 450°C. A composit target of Y₁Ba₂Cu₃O_7–x is evaporated by an excimer laser in the presence of an oxygen plasma. Plasma at 1-m Torr oxygen backpressure is triggered and sustained by the laser. Superconducting films of 0.5-μm thickness deposited on SrTiO₃ (110) showed a zero resistance at 85 K. Critical currents by transport method at 80 K was ~10⁵ A/cm².² On Si and GaAs, ultrathin MgO layers were deposited, using the same technique, prior to the deposition of Y₁Ba₂Cu₃O_7–x. This layer helps to reduce the diffusion as well as to form the superconducting orthorhombic structure. Auger sputter depth profiles of these films reveal the sharp interfaces with very low diffusion.

© 1988 Optical Society of America