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Non-invasive Measurements of the Thickness of YBCO Thin Films by Using Microwave Resonators: Roles of the Uncertainty in the Calibration Film Thickness  

Kim, Myung-Su (Department of Physics and Center for Wireless Transmission Technology, Konkuk University)
Jung, Ho-Sang (Department of Physics and Center for Wireless Transmission Technology, Konkuk University)
Yang, Woo-Il (Department of Physics and Center for Wireless Transmission Technology, Konkuk University)
Lee, Sang-Young (Department of Physics and Center for Wireless Transmission Technology, Konkuk University)
Publication Information
Progress in Superconductivity / v.14, no.1, 2012 , pp. 45-51 More about this Journal
Abstract
Microwave metrology for the thickness of metallic or superconductive films provides a new way to measure the film thickness in a non-invasive way by using microwave resonators, with the measurement accuracy affected by standard uncertainties in the resonator quality factor, temperature-dependent resonant frequency and the dimensions of the resonators. Here we study effects of the standard uncertainty in the thickness, $t_{cal}$, of a calibration $YBa_2Cu_3O_{7-{\delta}}$ (YBCO) film on the measured thicknesses, $t_{RF}$, by using a ~ 40 GHz microwave resonator. For the study, we used five YBCO films having the thicknesses of 70 - 360 nm, for which relative standard uncertainties in $t_{RF}$ due to that in $t_{cal}$ are obtained. The standard uncertainty in $t_{cal}$ was determined with the surface roughness of the film taken into account. It appeared that relative standard uncertainty in $t_{cal}$ significantly affects the $t_{RF}$ values, with the values of 1% (5%) in the former resulting in those of 1-2% (5-9%) for the latter at 10 K. Our results show that, for realizing relative standard uncertainties less than 5% in $t_{RF}$ for all the YBCO films, the surface roughness of the calibration films should be small enough to realize a relative standard uncertainty of less than 2.7% in $t_{cal}$.
Keywords
Film thickness; uncertainty; microwave; dielectric resonator; surface resistance;
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