| Popis: |
Microwave stripline resonator measurements are presented of Rs on large-area YBCO (Y1Ba2Cu3O7-x) films sputter deposited on cleaved MgO substrates. Dependence of Rs on temperature, frequency, and applied input power was determined. The films exhibited excellent dc properties with typical Tcs equals approx. 85 K, and Jcs equals 1 MA/cm2 at 77 K. At 1.2 GHz the inferred microwave Rs equals approx. 100 (mu) (Omega) at 4.2 K and Rs equals approx. 2 m(Omega) at 78 K for these same films. Losses in the patterned YBCO center strips showed large changes over an 80 dBm range for input power. These patterned center strips exhibited a much stronger dependence on input power than did unpatterned ground planes. This may be related to peak currents and high Hrf fields inside the stripline near the edges of the patterned center strip. Film degradation due to environmental effects has also been observed, with films stored for over 6 months degrading by a factor of two in Rs when retested. With respect to frequency, Rs approximates an f2 dependence when higher harmonics of the resonator are measured on these YBCO films. |
