High temperature superconducting films on flexible substrates for cryoelectronics

Abstract

High temperature superconducting (HTS) films on flexible, low loss, low thermal conductivity substrates offer unique advantages to transmit multichannel digital data with low signal attenuation for cryoelectronic applications. Polycrystalline, flexible yttria stabilized zirconia (YSZ) with a low thermal conductivity of 0.015 W/cm K, a low RF loss of 4×10 −4 (at 77 K, 5 GHz) and a relatively low dielectric constant of 28 is an excellent choice as a substrate if high quality HTS films can be developed with desirable RF properties. This paper presents recent data obtained on biaxially textured Y 1B 2C 3O 7− x (YBCO) films deposited on polycrystalline YSZ substrates with a biaxially-textured YSZ template. YSZ structural templates were developed by Ion beam-assisted pulsed laser deposition (PLD). YBCO films were deposited by PLD. The biaxially textured YBCO films exhibit in-plane (Phi-scans) FWHMs of ∼7°. The transition temperatures ( T c's) of the films are in the range 88–89 K with transition widths of 0.5 K. The critical current densities ( J c's) measured at 77 K, zero field, are in the range of 2×10 6 A/cm 2. The surface resistance of the films measured at 77 K, 10 GHz is 700 μΩ indicating a low microwave loss in these films. The high materials quality obtained in these HTS films on polycrystalline substrates can be used in fabricating a variety of components for cryoelectronic applications.