Experimental evidence for Coulomb charging effects in submicron Bi-2212 stacks

Focused ion beam (FIB) and ion milling techniques are developed for the fabrication of Bi2Sr2CaCu2O8+d (Bi-2212) stacked junctions with in-plane size L-ab ranging from several microns down to the submicron scale without degradation of superconducting transition temperature T-c. It is found that the behavior of submicron junctions (L-ab <1 mu m) is quite different from that of larger ones. The critical current density is considerably suppressed, the hysteresis and multibranched structure of the current-voltage (I-V) characteristics are eliminated, and a periodic structure of current peaks appears reproducibly on the I-V curves at low temperatures. The period Delta V of the structure is consistent with the Coulomb charging energy of a single pair, Delta V=e/C, where C is the effective capacitance of the stack. It is considered that this behavior originates from the Coulomb blockade of the intrinsic Josephson tunneling in submicron Bi-2212 stacks. (C) 1999 American Institute of Physics. [S0021-3640(99)01501-7].