Pulsed laser deposition of Y1Ba2Cu3O7- delta films on polycrystalline metallic substrates with TiN buffer layers

Abstract

Deposition of high-quality Y1Ba2Cu3O7- delta (YBCO) thin films on technologically important substrates such as stainless steel or high-temperature structural Ni-based superalloys is a difficult problem due to inherent interdiffusion problems between substrates and superconducting overlayers. To overcome this difficulty the concept of the buffer layer has been utilized and good quality YBCO thin films have been fabricated on Hastelloy (C), Inconel (600) and stainless steel (304) with titanium nitride (TiN) buffer layers. TiN is an excellent choice as a barrier layer on these metallic substrates due to low diffusivity, high thermal stability and thermal coefficient of expansion matching with the substrates. Because of the matching of the thermal expansion coefficient of TiN ( approximately (8.0-9.0)*10-6 K-1) with substrates ( approximately (9-10)*10-6 K-1) and YBCO ( approximately (12-13)*10-6 K-1) and its diffusion barrier characteristics, good quality high-Tc films have been grown on all substrates by single-chamber in situ laser processing at 600 degrees C. The films were characterized by X-ray diffraction, four-point AC electrical resistivity, scanning electron microscopy and Auger electron spectroscopy (AES) techniques. AES depth profiling indicated no interdiffusion of Fe across the interface of TiN and substrates. c-axis-oriented good quality thin films (zero resistance above liquid nitrogen temperature and Jc approximately 104-105 A cm-2 at 77 K) were obtained on these substrates. Optimization of laser deposition parameters to obtain superconducting thin films on metallic substrates for practical applications will be discussed in this paper.