Principle of photothermal radiometry. The one-dimensional two-layered model (layer 1 = YBCO thin film, layer 2 = MgO substrate, and backing material = acrylic resin) is applied.
The present experimental apparatus based on the photothermal radiometry for the measurement of thermal conductivity of YBCO thin films.
X-ray diffraction pattern of YBCO thin film (1000 nm nominal thickness) by XRD. The strong sharp peaks (001) to (007) are derived from the c-axis crystal orientation. On the other hand, polycrystalline peaks (102) and (115) are not observed.
Experimental results of phase lag versus frequency for YBCO thin film (1000 nm nominal thickness).
Thickness dependence of the thermal conductivity of YBCO thin films in comparison with the probable range for single crystal values near room temperature. The present experimental results exhibit apparently positive film thickness dependence, and their absolute values are less than half of those for single crystal at the smallest thickness.
Ratio of thermal conductivity in the c-axis direction of YBCO thin films to the corresponding bulk value, , as a function of film thickness in comparison to the calculated thickness dependence curves using Eqs. (14) to (17) with the possible mean free path as an adjustable parameter. Plots are the experimental results for thin films divided by .
YBCO film thicknesses measured by laser microscope and their critical temperatures.
Optical constants of the present YBCO thin films at 790 nm.
Experimental results of out-of-plane thermal conductivity of YBCO thin films.
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