The capacitance of bicrystal Josephson junctions deposited on SrTiO/sub 3/ substrates

Abstract

We have investigated the capacitance of grain boundary Josephson junctions deposited on symmetric 24/spl deg/ misoriented SrTiO/sub 3/ bicrystal substrates using hysteresis and Fiske resonances in their current voltage characteristics. Our measurements show that the total junction capacitance is proportional to the junction area. The capacitance per unit area is (140/spl plusmn/30) fF /spl mu/m/sup -2/ and this implies that the main effect of the large relative permittivity of the substrate is to scale-up the grain boundary capacitance by a factor of around 10. We also find that in the planar geometry of bicrystal grain boundary junctions the velocity of light in the junction depends upon film thickness.