FULL WAFER IN-SITU DEPOSITION OF THALLIUM LEAD SUPERCONDUCTORS

Thin films of (Tl,Pb)Sr2Ca0.8Y0.2Cu2O7, and (Tl,Pb)Sr2CuO5 can be grow n in a single step process which involves sputter deposition from a mi xed oxide target and simultaneous thermal evaporation of Tl2O. The use of a radiant heater has allowed extension of this in situ deposition process to full LaAlO3 and NdGaO3 wafers. Variations in the compositio n of the deposited film is < 4% across a 50 mm wafer while the thickne ss uniformity is approximate to 8%. The highest transition temperature for a (Tl,Pb)Sr2Ca0.8Y0.2Cu2O7 film thus far is 83 K. The RMS surface roughness of (Tl,Pb)Sr2CuO5 films is uniform across the wafer and app roximately 1% of the film thickness for films 20 to 100 nm thick.