Bi-Sr-Ca-Cu-O superconducting thin films perpared on the MgO (100) single crystal by metal organic chemical vapor deposition. As a precursor, $Bi(ph)_3$ [or $Bi(dpm)_3$], $Sr(dpm)_2$, $Ca(dpm)_2$, and $Cu(dpm)_2$ were used. In this study, the effect of deposition temperature, oxygen flow rate( oxygen partial pressure ) and cooling rate on the formation of the Bi-Sr-Ca-Cu-O superconducting phase and microstructure were investigated.
We could abtain high quality thin films when triphenylbismuth [$Bi(ph)_3$] was used as Bi source compared with dipivaloylmetanato-bismuth [$Bi(dpm)_3$]. Because triphenylbismuth is more stable vapor pressure at bubbling temperature and easier composition control of film. The vapor pressure of the metalorganic sources were strongly dependent on the bubbling temperature, and the optimal bubbling temperature of each source material was $Bi(ph)_3=120\circ\C$, $Sr(dpm)_2=240\circ\C$, $Ca(dpm)_2=202\circ\C$ and $Cu(dpm)_2 = 120℃.
Deposition temperature was great effective parameter on superconducting phase formation and microstructure, and the deposition temperature of low $T_c$ phase decreased with decreasing the oxygen partial pressure. Also, cooling rate was important variable on superconducting phase formation and microstructure. From this result, we know that superconducting phase is transformed during the cooling after formation of each oxide or its compound at deposition time, though some part of each evaporated source directly formed superconducting phase in the reactor. Best result up to date, abtained from a film grown at 820℃ and 1℃/min cooling rate, show 76K $T_{c(zero)}$ and 4000 A/㎠ critical current density.
