LASER DEPOSITION AND PATTERNING OF HIGH-TEMPERATURE SUPERCONDUCTING THIN-FILMS

Thin films (2-3 μm) of the high temperature superconducting ceramic Bi-Sr-Ca-Cu-O have been successfully deposited onto MgO substrates using a 'free lasing' infra-red Nd:YAG laser. These films show metallic resistance behavior, with superconducting transitions starting at about 90K and reaching zero resistance at 80K. The post deposition bake cycle was optimized and the dependence of electrical behavior upon deposition temperature was investigated. It was found that films deposited on cold substrates gave bismuth rich films, whilst films deposited on hot (>500°C) substrates gave bismuth poor films. The optimum temperature for accurate stoichiometric transfer of material was found to be 450°C. The films were subsequently patterned using a laser etch 'direct write' technique to form constrictions through which the critical current could be measured. Values as high as 34,000 Acm-2 were obtained.