Optical Response and Heat Characteristics in Y1Ba2Cu3O7-δ Microbridges with Different Surface Morphologies

Abstract

Y1Ba2Cu3O7-δ (YBCO) films with different surface morphologies have been used to study the dependence of the bolometric effect on the precipitates on the films. Films were patterned into microbridge bolometers with 25 µ m width and 650 µ m length. Although these microbridges had different T co (R=0), they had similar transition widths of about 1.8–2 K and similar ( dR/ dT) max values of about 71–78 Ω/ K. The precipitate coverages were varied from 0% to 100%. The photoresponses decreased exponentially from 2300 to 431 V/W with increasing precipitate coverage. We propose that the precipitate can be regarded as a low thermal conductive layer. This layer absorbed the incident light and preserved the thermal energy in it before passing it to the YBCO background layer. The modulated AC thermal signal ΔT is, therefore, suppressed by this layer such that a small signal is detected in the YBCO film. The noise equivalent power, however, increased with precipitation coverage; this implies an enhanced scattering of the superconducting carrier to the precipitates. The best values of noise equivalent power (NEP) and the detectivity (D*) in the present study were about NEP ≦5×10-12 W·Hz-0.5 and D* ≧109 cm·Hz0.5·W-1.