Measurements of dielectric constants and surface resistance for millimeter and submillimeter wavelength region using Josephson effect

Abstract

AbstractJosephson junctions with microstrip resonators fabricated. By observing the current steps caused by the mutual interaction between the high‐frequency current due to the ac Josephson effect and resonator, the dielectric constants of the dielectric thin films (a‐Si, SiO, and SiO2) and surface resistance of an Nb thin film at 4.2 K in the millimeter and submillimeter wavelength region were evaluated. As a result, it was found that this method was effective in determining the dielectric constant and surface resistance.In the device used, a Josephson junction was placed at the center of the microstrip resonator. the resonator length was varied from 217 to 2740 μm, the measurements were carried out at a frequency ranging from about 30 to 310 GHz, while the device was biased with dc voltage. the relative dielectric constants of the materials were rather independent of the frequency, where Ωa‐Si = 14.5 ± 0.5, ϵSiO 5.5 ± 0.4, and ϵSiO2 = 4.4 ± 0.4. the surface resistances of the Nb thin films were 1 to 6 mω when the frequencies were 70 to 180 GHz.