Synthesis and Investigation of Superconducting Bi-Sr-Ca-Cu-O Thin Films with 2212-Like Structure and Superconducting Transitions at 95 K

ABSTRACTVarious compositions Bi-Sr-Ca-Cu-O thin films having 2212–1 ike structure have been synthesized on MgO substrates using Molecular Beam Epitaxy. Four Knudsen metal sources were utilized to prepare alloy films which were subsequently post annealed in air atmosphere. Quenching of the films from the annealing temperature, 800°C-820°C, increased the superconducting transition temperature Tc. The highest Tcs, 90 K - 95 K, were attained for compositions with slightly lower Ca and Sr content if compared to the nominal 2212 and 2223 ones. Plasma frequency of free carriers, ωp, determined from optical reflectivity measurements have been found to increase with the average density of CuO2 units. However, no substantial shift ofωp was displayed by the highest Tc films.