G. Malandrino et al., TLBACACUO SUPERCONDUCTING THIN-FILMS VIA METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION (MOCVD) AND THALLIUM VAPOR DIFFUSION, Nuovo cimento della Societa italiana di fisica. D, Condensed matter,atomic, molecular and chemical physics, biophysics, 16(12), 1994, pp. 1953-1959
Superconducting thin films of the TlBaCaCuO family have been prepared
through a combined approach of MOCVD and thallium vapour diffusion. A
three-step process has been adopted involving i) the synthesis of Ba-C
a-Cu-O films by MOCVD using <<second-generation>> barium and calcium s
ources, ii) the hydrolysis of the fluoride phases by annealing in wate
r vapour-saturated oxygen and iii) the annealing in the presence of a
thallium source. Reproducible results, in terms of phase formation, ar
e discussed depending on the different conditions of the preannealing
process. The superconducting films consist predominantly of single-pha
se Tl2Ba2Ca2Cu3Ox(2223). Preferential orientation of the crystallite c
-axes perpendicular to the substrate surface has been observed. The fi
lms exhibit superconducting onset temperatures of 115-120 K with zero
resistance higher than 100 K.