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High temperature superconducting YBa2Cu3O7-δ thin flims and bolometers
In this work, we report the results on the response characteristics of high temperature superconducting bolometers under the infrared and optical radiation. The bolometers were made of YBa2Cu3O7-. (YBCO) thin films deposited on <100>-oriented and 10x10x1-0.5 mm3 sized single crystal MgO substrates by using DC inverted cylindrical magnetron sputtering (ICMS) technique with 200 nm thickness. The thin films were characterized in detail by employing structural (XRD, SEM, EDX, and AFM), magnetic (.-T) and electrical (R-T) measurements. We have investigated effects of temperature and modulation frequency on the magnitude and phase of the infrared response of the both large and small area bolometers. Dependence of the phase and magnitude of the response of MgO substrate YBCO edge transition bolometers to a near infrared radiation on the superconducting transition width has also been investigated in this work. We have observed that the superconductivity transition width has major effects on the response of the bolometers such as; on a dip of the phase of the response versus modulation frequency curve around 1 Hz, the rate of decrease of the magnitude of the response, and dependence of the phase of the response on temperature at mid-range modulation frequencies. Wavelength dependence of the photoresponse of YBCO edge transition bolometers has been studied. It was observed that the optical response of the devices was almost independent of the wavelength of incident light from 0.4 .m to 0.73 .m. Here we present the analysis and the possible mechanisms that can affect the response of the bolometers in the superconducting transition region.