Development of conducting buffer architectures using cube textured IBAD-TiN layers
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1150-RR04-01
Development of conducting buffer architectures using cube textured IBAD-TiN layers Ruben Hühne1, Konrad Güth1, Martin Kidszun1, Rainer Kaltofen1, Vladimir Matias2, John Rowley2, Ludwig Schultz1 and Bernhard Holzapfel1 1
IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
2
Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
ABSTRACT Ion-beam assisted deposition (IBAD) offers the possibility to prepare thin textured films on amorphous or non-textured substrates. In particular, the textured nucleation of TiN is promising for the development of a conducting buffer layer architecture for YBCO coated conductors based on the IBAD approach. Accordingly, cube textured IBAD-TiN layers have been deposited reactively using pulsed laser deposition on Si/Si3N4 substrates as well as on polished Hastelloy tapes using different amorphous seed layers. Metallic buffer layers such as Au, Pt or Ir were grown epitaxially on top of the TiN layer showing texture values similar to the IBAD layer. Smooth layers were obtained using a double layer of Au/Pt or Au/Ir. Biaxially textured YBCO layers were achieved using SrRuO3 or Nb-doped SrTiO3 as a conductive oxide cap layer. Finally, different amorphous conducting seed layers were applied for the IBAD-TiN process. Highly textured TiN films were achieved on amorphous Ta0.75Ni0.25 layers showing a similar in-plane orientation of about 8° as on standard seed layers. INTRODUCTION Ion beam assisted deposition (IBAD) of biaxially textured buffer layers is one of the major routes for the preparation of suitable templates for YBCO coated conductors [1,2]. In particular, the deposition of highly textured MgO layers has gained a lot of interest as the desired cube texture is already created during nucleation within the first 10 nanometres making this process very time-efficient [3]. It was shown recently that other materials having a rocksalt structure, for example TiN, can be textured in a similar way [4]. One major advantage of TiN is its good electrical conductivity. This would enable the realization of a conductive buffer architecture within the IBAD approach leading to an electrical connection between the superconducting layer and the thick metal substrate in order to avoid thermal destruction of the superconductor in case of an overcurrent situation. So far only non-conducting buffer architectures have been prepared based on textured IBAD-TiN layers [5]. Two major challenges need to be solved in order to realize a completely conducting buffer layer stack: (i) an electrically conductive amorphous or nanocrystalline seed layer has to be applied on the metal tape; (ii) additional conducting buffers have to be deposited on the IBAD layer in order to reduce the significant lattice mismatch between TiN (lattice parameter a = 0.424 nm) and YBCO (a ≈ b ≈ 0.386 nm) and to avoid the oxidation of the nitride layer. Different noble metals were tested for their suitability as buffers on TiN. Among them, gold (a = 0.408 nm) shows a good epitaxial g
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