Browsing by Subject "Magnesia"

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Open Access
Effect of the superconductivity transition on the response of YBCO edge transition bolometers
(2003) Bozbey, Ali; Fardmanesh, Mehdi; Askerzade, I. N.; Banzet, M.; Schubert, J.
Dependence of the phase and magnitude of the response of Y-Ba-Cu-O edge transition bolometers on the superconducting transition is studied. The responses of both large and small area devices were investigated and several anomalies are observed. The response of small area LaAlO3 devices considerably differed from that expected based on the dR/dT curve. This discrepancy is observed to be strongly dependent on the superconducting transition. Both the phase and magnitude/(dR/dT) of the response of the devices showed abrupt changes for below the Tc-onset when measured versus temperature, while the phase variation also showed strong dependence on the modulation frequency. We present the analysis and propose mechanisms responsible for the modulation frequency dependence of the response characteristics versus temperature, within the superconductivity transition region of the devices.
Open Access
Temperature dependence of the phase of the response of YBCO edge-transition bolometers: effects of superconductivity transition and thermal parameters
(Institute of Physics Publishing, 2003) Fardmanesh, M.; Askerzade, İ. N.
The variation of the phase of the response of YBCO edge-transition bolometers on crystalline MgO substrate is found to be dependent on the normal-superconducting transition. The phase of the response for T < Tc increased at low modulation frequencies where the thermal diffusion length into the sample substrate from the top absorbing YBCO film is longer than the substrate thickness. The substrate/cold-head boundary resistance mainly dominates the thermal conductance of our samples at low frequencies. This transition-dependent change of the phase of the response is interpreted to be due to the effects of the order parameter of the YBCO material on the phonon spectrum and hence the determining Kapitza boundary resistance. The phase of the response decreased at high modulation frequencies where the thermal diffusion length into the substrate is less than the substrate thickness. The results of our analytical model for the low modulation frequencies agree well with the measured values for temperatures close to the Tc-zero.