Jc. Booth et al., Simultaneous optimization of the linear and nonlinear microwave response of YBCO films and devices, IEEE APPL S, 9(2), 1999, pp. 4176-4180
We present results of a systematic study of the effect of film deposition t
emperature on both the linear and nonlinear response of superconducting YBa
2Cu3O7-delta (YBCO) thin films and devices at microwave frequencies. Measur
ements of the unpatterned films show that samples grown by pulsed laser dep
osition at a lower substrate temperature (740 degrees C) display a smaller
low-temperature residual surface resistance compared to films grown at a hi
gher substrate temperature (780 degrees C). However, the same films which d
isplay low residual surface resistance also show increased nonlinear effect
s (measured by third harmonic generation) at all temperatures. Analysis of
these results suggests that the increased defects present in the films grow
n at the lower deposition temperature are responsible for both the lower su
rface resistance and the higher third harmonic generation observed in these
samples. We discuss the consequences of these results for the simultaneous
optimization of both linear and nonlinear microwave properties of HTS thin
films and devices.