Y-Ba-Cu-O microstrip resonators on sapphire substrates

Abstract

We have measured very low microwave losses in Y-Ba-Cu-O fifth wave ring resonators. We deposited the Y-Ba-Cu- O film on (1012) non-buffered sapphire substrates and patterned microwave circuites. High-Tc microstrip resonators demonstrated best Q-factor greater then 800 at 31 GHz, corresponding to surface resistances less than 3,0 mOhm. Indetical copper resonator showed Q's of 500 and surface resistance of 27 mOhm. We show that the losses in the high loss samples can be accounted for by the presence of small fractions of c-axis-aligned grains highly misapplied in the plane of those films. Volume fraction of highly misagned c-axis-oriented grains as 3% lead to losses above 3 mOhm.