Highly oriented films of the high-Tc superconductor Bi 2Sr2CaCu2Ox have been prepared by a low-pressure organometallic chemical vapor deposition process using a mixture of ammonia and argon as the carrier gas together with Sr(dpm)2 (dpm-dipivaloylmethanate), Ca(dpm)2, Cu(acac)2 (acac-acetylacetonate), and triphenylbismuth as the organometallic precursors. By introducing ammonia into the carrier gas, a significant improvement in the volatility and thermal stability of both Sr(dpm)2 and Ca(dpm) 2 is observed. Typical required source temperatures for Sr(dpm) 2 and Ca(dpm)2 with the introduction of ammonia are about 40-50°C lower than the source temperatures of the precursors without the introduction of ammonia. Enhancement of source volatility for Cu(acac) 2 is also observed. After annealing at 865°C in flowing oxygen, the films consist predominantly of the Bi2Sr2CaCu 2Ox phase and exhibit high preferential orientation of the crystallite c axes perpendicular to the substrate surface. Four-probe resistivity measurements indicate the onset of film superconductivity at ∼110 K and zero resistivity achieved at 74 K.
ASJC Scopus subject areas
- Physics and Astronomy(all)