3570 IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 13, NO. 2, JUNE 2003 Accurate Microwave Technique of Surface Resistance Measurement of Large-Area HTS Films Using Sapphire Quasi-Optical Resonator Nickolay Cherpak, Senior Member, IEEE, Alexander Barannik, Yury Filipov, Yury Prokopenko, and Svetlana Vitusevich Abstract—We have developed a surface resistance ( ) measurement technique for large-area high-temperature super- conducting (HTS) films using quasioptical dielectric resonators (QDR) with HTS endplates (quasioptical Hakki-Coleman resonators). In this technique, the highest modes, namely whis- pering-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. Index Terms—Films, millimeter wave measurements, resonator, superconductors (high-temperature). I. INTRODUCTION A MONG a large variety of the resonant measurement sys- tems, special emphasis is made on resonators developed for surface resistance, , characterization of HTS unpat- terned films [1]. The -measurements are important both for fundamental physical studies and technical applications. The -values of HTS films are sensitive to any kind of deffects in superconductors and to fabrication processes. By now, a number of groups have developed different techniques for the HTS film -measurement [2]. The accuracy and sensitivity of the HTS film -measure- ment depend on relation between losses caused by the resonator different parts. Physical studies and engineering developments using HTS materials call for standard techniques of -mea- surement which should ensure high sensitivity, low error of mea- surements and relative ease of a measurement process [3]. For the classical microwave band (with frequencies less than 25 GHz,) the standard technique based on a sapphire Manuscript received August 6, 2002. This work relates to Department of the Navy Grant N00014-02-1-4072 issued by the Office of Naval Research Inter- national Field Office. The United States Government has a royalty-free license throughout the world in all copyrightable material contained herein. N. Cherpak, A. Barannik, Y. Filipov, and Y. Prokopenko are with Usikov Insti- tute of Radiophysics and Electronics, National Academy of Sciences, Kharkiv, 61085, Ukraine (e-mail: cherpak@ire.kharkov.ua; prokopen@ire.kharkov.ua). S. Vitusevich is with the Institut für Schichten und Grenzflächen Forschungszentrum, Jülich, D-52425, Germany (e-mail: s.vitusevich@ fz.-juelich.de). Digital Object Identifier 10.1109/TASC.2003.812400 (Al O ) resonator with the lower mode oscillations has been proposed [4]. Of two basic types of a dielectric resonator (DR), a Hakki-Coleman resonator [5]. has the advantage of permitting the calculation of the total energy dissipation. In the millimeter (mm) waverange ( is higher than 25 GHz), the dimensions of DR’s with the lower-mode oscillations (waves) become unacceptably small and their quality factor, , falls. The highest azimuthal order modes, i.e., whispering gallery (WG) waves, have the highest -quality factor. The de- vices are quasioptical, so DR’s with two conducting endplates (CEP) and WG waves are, as a matter of fact, the quasioptical (QDR) Hakki-Coleman resonators [6]. They have acceptable dimensions in mm waverange and are promising for using in resonant structures with HTS films. A consistent analysis of electrodynamic properties of the QDR with CEP in a case of anisotropic dielectric [7] provides theoretical foundation for the QDR-based determination. The present work deals with the following problems: i) quan- titative evaluation of radiation, dielectric and (super)conductor energy losses in QDR with CEP; ii) experimental justifica- tion of validity of the proposed -measurement technique; iii) -measurement of HTS large-area films in the mm wave range using QDR with CEP. II. THEORETICAL RELATIONSHIPS FOR THE -FACTOR OF THE QUASI-OPTICAL DIELECTRIC RESONATOR WITH CONDUCTING ENDPLATES In accordance with a sum rule for inverse -values, the ex- pression for eigen -factor of QDR with CEP can be written as (1) where the coefficients and show contribution of dielectric and conductor losses in the energy total loss in QDR, is the dielectric loss tangent, is the radiation loss quality, and are the surface resistances of the HTS film and normal metal CEP’s. As is shown below, one can neglect in the QDR with CEP with large diameter. In a case when both CEP’s are formed of HTS samples (normal metal), we obtain (2) From the electrodynamic solution of the field structure in the QDR with CEP, the expression for -quality is obtained [7] (3) 1051-8223/03$17.00 © 2003 IEEE