CVD of Bi-Sr-Ca-Cu-O Thin Films
We developed a chemical vapor deposition (CVD) method for high-Tc superconducting Bi-Sr-Ca-Cu-O thin films, and obtained a high-Tc phase (about 110 K) without postannealing in an atmosphere containing oxygen. Films were deposited on (001) MgO substrates in He in an open-tube reactor with O2 and/or H2O oxidizing agents. The source materials --anhydrous metal halides such as BiCl3, SrI2, CaI2, and CuI -– were evaporated in the CVD system to be used as source gases. The deposition temperature was between 700°C and 850°C. The average deposition rate was about 1.5 nm/min and the average film thickness was about 0.1 μm. Films were a mixture of low-Tc (about 80 K) and high-Tc (about 110 K) phases. Their C-axis orientation was perpendicular to the substrate. Their electrical resistance decreased abruptly below 115 K and the zero-resistance temperature was around 98 K. A critical current density of about 1.7 x 104 A/cm2 was obtained at 4.2 K. The O2 in the CVD atmosphere played an important role in determining the phase of films at higher temperature depositions.
KeywordsChemical Vapor Deposition Deposition Temperature Source Zone Deposition Zone Film Characteristic
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