MEASUREMENTS OF DIELECTRIC-CONSTANTS AND SURFACE-RESISTANCE FOR MILLIMETER AND SUBMILLIMETER WAVELENGTH REGION USING JOSEPHSON EFFECT

Josephson junctions with microstrip resonators fabricated. By observin g the current steps caused by the mutual interaction between the high- frequency current due to the ac Josephson effect and resonator, the di electric 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 a nd submillimeter wavelength region were evaluated. As a result, it was found that this method was effective in determining the dielectric co nstant and surface resistance. In the device used, a Josephson junctio n was placed at the center of the microstrip resonator. The resonator length was varied from 217 to 2740 mu m, the measurements were carried out at a frequency ranging from about 30 to 310 GHz, while the device was biased with de voltage. The relative dielectric constants of the materials were rather independent of the frequency, where epsilon(a-Si ) = 14.5 +/- 0.5, epsilon(SiO) = 5.5 +/- 0.4, and epsilon(SiO2) = 4.4 +/- 0.4. The surface resistances of the Nb thin films were 1 to 6 m Om ega when the frequencies were 70 to 180 GHz.