Low-loss substrate for epitaxial growth of high-temperature superconductor thin films

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Abstract
A perovskite‐like single‐crystal substrate material has been investigated that simultaneously permits epitaxialgrowth of 1‐2‐3 superconductorfilms and possesses desirable rf properties of low dielectric constant and loss tangent. The lattice constant of 3.792 Å provides a lattice match to within 1% of the a axis of 1‐2‐3. Sputtered films of erbium‐barium‐copper‐oxide have been produced on (100) LaAlO3 substrates that exhibit sharp resistive transitions at 90 K (ΔT=1K), bulk superconductivity as determined by ac susceptibility measurements, and nearly single‐crystal growth as evidenced by x‐ray diffraction and high‐resolution scanning electron microscopy. The high‐frequency dielectric properties of LaAlO3 were experimentally investigated at several temperatures. The low‐frequency dielectric constant was measured to be 15 and the microwave loss tangent ranged from 6×10− 4 at room temperature to 5×10− 6 at 4 K.