Laterally resolved microwave surface-resistance measurement of high-T-c superconductor samples by cavity substitution technique

Microwave surface impedance measurement of a high-temperature superconducto r (HTS) is a sensitive probe to test its quality, particularly if a microwa ve device is to be fabricated. Most microwave characterization employs reso nance techniques in which the components of the surface impedance are extra cted from the measured Q value and the shift in the resonance frequency. In this paper, we present a modification of the widely used complete end-plat e substitution technique to measure the surface resistance of samples havin g dimensions smaller than the dimension of the end plate at 20 GHz, as well as to facilitate the laterally resolved surface resistance measurement of large-area HTS samples. From the knowledge of the electromagnetic-field con figuration in a TE011-mode cylindrical cavity, the loss contribution from t he HTS sample is analyzed theoretically and measured experimentally in the temperature range of 20-100 K, The design of the cavity is discussed to opt imize the sensitivity of the measurement by the placement of the sample and to maximize the difference in the measured Q value.