SPONTANEOUS PATTERNING IN HIGH-TEMPERATURE SUPERCONDUCTING FILM BY LIQUID-GAS-SOLIDIFICATION PROCESSING

Without any post physical or chemical patterning a Tl-base high temper ature superconducting film has been observed to pattern spontaneously on SrTiO3 (100) by liquid-gas-solidification process. The film exhibit s the morphology of a microelectric network in which the directions of growth of the crystal walls follow the directions of the SrTiO3 (100) substrate. The crystal walls consisting of Tl-1223 and Tl-1212 phases are 0.25-1 mum wide, 2 mum high, and a few millimeters long. These wa lls are proposed to grow from independent nucleation sites and coalesc ence to form semiconductive junctions. The network exhibits a supercon ducting transition onset at 113 K and approaches zero resistance at 95 K. Below 95 K, the resistance increases exponentially with decreasing temperature. This strongly suggests that the films form a natural sup erconductor/semiconductor/superconductor junction array.