SURFACE-MORPHOLOGY AND ELECTRICAL-PROPERTIES OF BI-SR-CA-CU-O THIN-FILMS DEPOSITED BY REACTIVE SPUTTERING FROM MULTIPLE TARGETS

Smooth, superconducting films of Bi2Sr2CaCu2O8+delta have been prepare d by reactive sputtering from elemental targets in the presence of ozo ne. The influence of substrate temperature, deposition rate, and ozone pressure on the resulting films are discussed. Films deposited on SrT iO3 substrates are c-axis oriented and featureless for substrate tempe ratures below 710-degrees-C. Above this temperature, small inclusions of CuO appear. Films on MgO exhibit mixed a-axis and c-axis orientatio n below about 710-degrees-C, and inclusions of CuO above this temperat ure. The temperature at which this transition occurs increases with in creasing deposition rate. T(c) increases and then decreases sharply wi th decreasing oxygen content. The oxygen partial pressure correspondin g to the maximum T(c) of 77 K is well above the thermodynamic stabilit y limit for Bi2Sr2CaCu2O8+delta, suggesting that an optimum carrier co ncentration has been achieved for these films.