Observation of strong Coulomb blockade in resistively isolated tunnel junctions

We report measurements of the Coulomb-blockade current in resistively isola ted(R-Isol 2 much greater than h/e(2)) tunnel junctions for the temperature range 60 mK < T < 230 mK where the charging energy E-c is much greater tha n the thermal energy. A zero-bias resistance Ro of up to 10(4) R-T (the tun nel resistance of the bare junction) is obtained. For eV much less than E-c , the I-V curves for a given R-Isol scale as a function of V/T, with I ex: V-alpha(RIsol) over a range of V. The data agree well with numerical calcul ations of the tunneling rate that include environmental effects. (C) 1998 E lsevier Science Ltd. All rights reserved.