In-situ deposition and processing of YBa/sub 2/Cu/sub 3/O/sub 7-x/ films and multilayers for optoelectronic devices

In situ direct deposition at approximately 700 degrees C of thin YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconductive films and multilayers has been done by three techniques using stoichiometric YBa/sub 2/Cu/sub 3/O/sub 7-x/ sintered targets. Excimer laser ablation in a DC magnetron system with hollow and planar targets leads to 0.5-, 1.2-, and 2.5-in diameter uniformly superconductive layers under static conditions. High critical current densities (>10/sup 6/ A cm/sup 2/ at 77 K) associated with low resistivity and good epitaxial behavior are achieved on top of MgO, SrTiO/sub 3/, LaAlO/sub 3/, and YSZ single-crystal wafers. High-quality c-oriented films (T/sub c/>80 K) are routinely obtained by means of a DC magnetron on large sapphire (>2 in) substrates covered by a YSZ RF sputtered buffer layer. The infrared properties of such films have been checked at 1.15- mu m wavelength. In order to achieve active devices (such as optical detectors and high-frequency mixers), small (<10- mu m/sup 2/) YBa/sub 2/Cu/sub 3/O/sub 7/-YSZ-Ag tunnel junctions and arrays have been successfully patterned in the superconductor/insulator/normal-metal trilayers using SNOP (selective niobium overlap process).