BSCCO precursor films

The electrodeposited Bi2Sr2CaiCu2Ox (BSCCO) precursor films were obtained by co-electrodeposition of the constituent metals using nitrate salts dissolved in DMSO solvent. The electrodeposition was performed in a closed-cell configuration at room temperature ( 24°C). The cation ratios of the electrodeposition bath were adjusted systematically to obtain BSCCO precursor compositions. A typical electrolyte-bath composition for the BSCCO films consisted of 2.0-g Bi(N03)3-5H20,1.0-g Sr(N03)2, 0.6-g Ca(N03)2-4H20, and 0.9-g Cu(N03)2-6H20 dissolved in 400 mL of DMSO solvent. The substrates were single-crystal LAO coated with 300 A of Ag. 

Zhang et al. at Northwestern University have reported the successful CVD growth of superconducting BSCCO films on polycrystalline silver substrates [247, 248]. After deposition at 625 °C using N2O as the reactant gas, the BSCCO precursor films were subjected to a flowing oxygen post-anneal at 650°C for 1 h, followed by 865°C for 1 h. Magnetically-derived Tj. values up to 80 K and zero-field values of 3.9 x 10 Acm" at 5.5 K were determined for these Bi-2212 phase films. 

Nemoto et al. at Nissan reported the first CVD growth of BSCCO films using fluorocarbon-based chelates [240]. Triphenyl bismuth and the hexafluoroacetylacetonato complexes of Sr, Ca, and Cu were used as precursors in oxygen at a 20 Torr system pressure with a substrate temperature of 600°C to give amorphous, insulating films. After an air anneal at 830°C for 1 h, the films were c-axis oriented Bi-2212 with 7(. = 50 K. Researchers at Advanced Technology Materials deposited amorphous BSCCO(F) films at 500 °C under 2 Torr pressure using the fluorinated complexes Ca(fod)2, Sr(fod)2, and Cu(hfa)2 as well as Bi(ph)3 as precursors [241]. Fluorine was... 

BSCCO Films by CVD Using Fluorinated Metal-Organic Precursors. . 115... 

The first in situ growth of BSCCO by MOCVD was reported by Endo et al. at the Electrotechnical Laboratory [222]. In this and all further reports, these researchers employed Bi(ph)3, Sr(dpm)2, Ca(dpm)2, and Cu(dpm)2 as the volatile precursors. In situ growth was achieved by deposition under 50Torr total system pressure at 800 °C with oxygen as the reactant gas. A temperature dependence of in situ c-axis oriented phase formation was noted as follows (i) = 700°C gave Bi-2212 films (ii) =... 

Researchers at the University of Tokyo have reported the low temperature in situ growth of superconducting BSCCO films by CVD [238]. Bi(ph)j, Sr(dpm)2, Ca(dpm)2, and Cu(dpm)2 precursors were employed with oxygen at a substrate temperature of 550 °C and a system pressure of 2Torr, thereby producing Bi-2212 films with 7]. = 65 K. In another report, Bi-2212 phase films were grown at a deposition temperature of 500°C by UV-photo-assisted CVD, however, no superconducting transition was noted down to 15 K [239]. 

The synthesis of fluorinated, volatile bismuth )3-diketonates for MOCVD was reported in a recent submission by Sievers et al. [243]. Bi(fod),i was isolated and characterized to be sufficiently volatile for CVD growth of bismuth films although no BSCCO film growth has yet been demonstrated. This report also provides an excellent survey of volatile bismuth metal-organic and organometallic precursor chemistry. 

Superconducting BSCCO films were produced in situ on 3" diameter sapphire substrates by plasma-enhanced halide LPCVD [266, 267]. Films consisting mainly of the Bi-2212 phase were deposited with metal halide precursors at 580°C under 0.1 Torr system pressure in the presence of a rf plasma. These films became superconducting at 70 K with = 2.5 x 10 Acm at 10 K. Plasma-enhanced halide LPCVD was also used to grow Bi-Sr-Ca-Cu-O/Bi-Sr-Cu-O superconductor-normal metal (S-N) heterostructures [259], HRTEM images showed the S/N interface to be atomically abrupt while variable temperature resistivity measurements gave T. = 75 K for the S/N heterostructure. 

Uppsala and Northwestern University, thermodynamic calculations were performed using Bi(ph)3, Sr(hfa)itet, Ca(hfa)2tet, and Cu(acac)2 as metal-organic precursors [126]. The experimentally observed phase stability of BSCCO for in situ CVD was in agreement with the calculated thermodynamic oxide stability diagrams [126]. These results indicate that thermodynamic modeling can be used as a guide for the optimization of CVD routes to complex metal oxide films. 

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