Studies on optical detection of Tc of Bi-Sr-Ca-CuO films

Polycrystalline films of Bi-Sr-Ca-CuO are deposited onto silver substrate using pulse electrodeposition technique and then electrochemically oxidised at room temperature. Resistivity is measured using four probe method and films show resistanceless state below 103K. This Ag/Bi-Sr-Ca-CuO junction gives certain potential - without passing any current through it - called contact potential (vc). Contact potential is sensitive to temperature as well as illumination and it leads to new optical method of determination of critical temperature of superconducting films. Critical temp. of Bi-Sr-Ca-CuO films detected by this optical method is 104K. Experimental procedure and results are discussed in depth in this paper. (author)