Bi-2212 films

Figure 7.13 TEM analysis of the ED Bi-2212 films on LAO (a) HRTEM, (b) clean interface, and (c) stacking fault (SF). [Reproduced with permission from Ref. 101. Copyright 2004 IOP Publishing Limited.]...

Chen, J. Bhattacharya, R. N. 2003. Growth of 1-2 xm thick biaxially textured Bi-2212 films on (1 0 0) LaA103 single crystal substrates by electrodeposition. Physics C 399 171-177. 

Bi-2223 films have been grown by laser ablation , sputtering MOCVD ", etc. Phase-pure Bi-2223 film is much more difficult to grow than comparable Bi-2212 film... 

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]. 

Advances have been also made in the fabrication ofBiSrCaCuO films. Bi-2212 is better than Bi-2223 for the fabrication of high-quality thin films due to its thermodynamic stability. Xhe most important issue in the fabrication of high-quality Bi-2212 films is to avoid the intergrowth of homologous structures such as Bi-2201 and Bi-2223. 

Two types of precursor can be used in CVD of superconducting mixed oxides metal halides and metal-organics The use of metal-organic molecules results in some carbon in the films, which can hinder performance, so metal halides gained popularity in early work. Halide precursors call for a much higher deposition temperature. In the case of metal halide reactions, the chemistry follows that presented earlier (see 17.2.5.2.2) but with multiple reactions occurring simultaneously. The gas phase composition and temperature are controlled to obtain the desired stoichiometry. An example of such a reaction would be that used to make Bi2Sr2CaCu20s+ c(or Bi-2212) at 760-820°C ... 

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... 

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. 

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. 

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