摘要
YBCO superconducting thin films with a precipitational free morphology and an extremely smooth surface of rms roughness less than 5 nm have been grown by an off-axis RF sputtering technique. The film was patterned into a 25 × 650 μm 2 microbridge by a conventional photolithography technique and has a superconducting transition T c0 of 76.1 K nearby the liquid nitrogen temperature. The transition temperature, the dR/dT value as well as the operating temperature T op of the microbridge can be tuned by the bias current. It means that the temperature control system can be substituted by a liquid nitrogen bath by choosing a proper bias current. The opto-electrical properties of the bolometer were measured by means of low power radiation sources, ≤ 0.08 J/cm 2 s, with wavelength from 0.633 to 3.5 μm. The bolometer has relative wide-stable operating temperature (77.1-77.7 K) and current (8 ± 1 mA) regions, and its responsivity is independent of the radiation wavelengths that proved itself to be a broad band detector. When a bias current of 8 mA and various sources modulated at 2 Hz were applied on the microbridge at 77.35 K, the responsivity of the bolometer could reach as high as 2.3 × 10 3 V/W at all wavelengths. At the same condition, the noise equivalent power (NEP) and detectivity (D *) have been measured to be 4.34 × 10 -12 W Hz -0.5 and 3 × 10 9 cm Hz 0.5 W -1 respectively.