Accurate microwave technique of surface resistance measurement of large-area HTS films using sapphire quasi-optical resonator

Abstract

Abstract-We have developed a surface resistance ( ) measurement technique for large-area high-temperature superconducting (HTS) films using quasioptical dielectric resonators (QDR) with HTS endplates (quasioptical Hakki-Coleman resonators). In this technique, the highest modes, namely whispering-gallery modes, in sapphire disk sandwiched between HTS films or between one HTS film and one Cu endplate are excited at K-band frequencies. The authors report on measurement results of surface resistance of 52 mm diameter high-quality YBCO thin films. The measurement results revealed that the technique is feasible for accurate -measurements of large-area thin films. The method is appropriate for standard measurement of at millimeter wave frequencies by analogy with classic DR-based microwave technique, although QDR-based technique has some fundamental differences.

Millimeter-wave surface impedance of optimally-doped Ba(Fe1−xCox)2Barannik1, Cherpak2, Tanatar3 et al. 2013Phys. Rev. BSelf Cite284320View full textAdd to dashboardCite

“…Unlike the case of the homogeneous sapphire disk QDR, where CEP Q −1 rad,0 < 10 −9 and radiation loss can be neglected [28], in the radially slotted QDR a value of Q −1 rad becomes comparable with other losses in Eqs. (4) and (5).…”

“…The resonator with conducting endplates (CEP) was developed earlier for the millimeter-wave impedance characterization of the cuprate high-T c films [28,29]. For study of iron-pnictides it was modified into a disk resonator with a radial slot as illustrated in Fig.…”

“…The coefficient A s can be calculated analytically by solving the resonator electromagnetics problem [28]. If the analytical solution cannot be found, the value of A s can be determined by a calibration procedure, using samples with known properties [29].…”

Microwave properties of HTS films: measurements in the millimeter wave range

“…13 In the case of the axially homogeneous HE ns0 mode, which is excited relatively easily, expressions for R Y 0 and R Y are cited in Ref. 6. The coefficient k is very close to 1 and the coefficient A s is shown in Fig.…”

“…5 We recently reported an accurate technique for the R s measurement of large-area HTS films using a sapphire quasioptical dielectric resonator ͑QDR͒ with conducting endplates ͑CEP͒. 6 In this approach, the WG modes are excited in a dielectric cylindrical disc sandwiched between HTS films or between one HTS film and one copper endplate ͑Fig. 1͒.…”