Surface morphology effect on the photoresponse of high temperature superconducting microbridges Available to Purchase

Three Y₁Ba₂Cu₃O_7−δ superconducting thin films with 20%, 60%, and 100% coverage of precipitates were fabricated into microbridges of 25×650 μm² by a conventional photolithography method. These microbridges exhibit a T_co(R=0) from 83.6 to 87.2 K and a transition width of about 1.8 K. These also have (dR/dt)_max values of about 71–78 Ω/K. We find that the fewer the precipitates on the film, the better the thermal conduction, and a larger responsivity (S) can be achieved. The best responsivity of 783 V/W measured at I_b=8 mA, T_op=86.8 K, and f=2 Hz for various wavelengths of light sources is obtained from the film with 20% precipitation. The photoresponse signals decay exponentially with the precipitation coverages, which indicates that these precipitates behave as thermal resistance layers that smooth out the ac incident signal, suppress the rise in microbridge temperature, and result in a smaller photoresponse signal for the bolometer.