Fabrication by Inclined-Substrate Deposition of Biaxially Textured Buffer Layer for Coated Conductors
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Fabrication by Inclined-Substrate Deposition of Biaxially Textured Buffer Layer for Coated Conductors U. Balachandran, B. Ma, M. Li, R. E. Koritala, B. L. Fisher, R. A. Erck, and S. E. Dorris Energy Technology Division, Argonne National Laboratory, Argonne, IL 60439 ABSTRACT Inclined substrate deposition (ISD) offers the potential for rapid production of high-quality biaxially textured buffer layers suitable for YBCO-coated conductors. We have grown biaxially textured MgO films by ISD at deposition rates of 20-100 Å/sec. Columnar grain structures with a roof-tile-shaped surface were observed in the ISD-MgO films. X-ray pole figure analysis revealed that the (002) planes of the ISD-MgO films are titled at an angle from the substrate normal. A small phi-scan full-width at half maximum (FWHM) of ≈9° was observed on MgO films deposited at an inclination angle of 55°. YBCO films were also grown on ISD-MgO-buffered Hastelloy C276 substrates by pulsed laser deposition. We obtained a critical current density of ≈2 x 105 A/cm2 at 77 K in self-field on 0.5-µm-thick, 0.5-cm-wide, 1-cm-long samples. This work has demonstrated that biaxially textured ISD MgO buffer layers deposited on metal substrates are promising candidates for fabrication of high-quality YBCO-coated conductors. INTRODUCTION The development of YBa2Cu3O7-δ (YBCO) coated conductor technology will make possible the design and fabrication of smaller, lighter, and more efficient power devices, such as motors, generators, transformers, transmission cables, and fault-current limiters, that can be operated at temperatures that approach the temperature of liquid nitrogen [1-3]. To meet the needs of the U.S. electric power industry, enormous effort has been expanded in the past few years to accelerate the processing, fabrication, and manufacturing of high-temperature superconductors and coated conducting wires [4]. Highly textured template films or buffer layers are necessary to successfully deposit biaxially aligned YBCO films on flexible metal substrates and thereby achieve high critical current density (Jc). Several techniques including ion-beam-assisted deposition (IBAD), rolling-assisted biaxially textured substrates (RABiTS), and inclinedsubstrate deposition (ISD), have been developed [5-7]. YBCO films have been deposited on the buffered substrates by pulsed laser deposition (PLD), chemical vapor deposition, or electronbeam (e-beam) coevaporation methods [8-10]. When compared with IBAD and RaBiTS, the ISD process produces textured films at high deposition rates (20-100 Å/sec) and is independent of recrystallization properties of the metallic substrates. It is also simpler (without the need of an assisting ion source) and easier to accomplish. Magnesium oxide (MgO) thin films deposited on inclined substrates were first observed to exhibit preferred orientation by Aboelfotoh in 1973 [11]. Recently, Bauer et al. reported the use of the ISD to fabricate MgO buffer layers for coated-conductor applications [12]. We grew biaxially textured MgO thin films on mechanically
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