We have studied electron tunneling in ultralow-capacitance silver particles sandwiched between artificial tunnel barriers. We have observed steps in the current-voltage characteristics of these systems with voltage widths of e/C (C being the capacitance of the particles), and associated current rises of e/RC. This represents the first observationof the so-called Coulomb staircase, expected for the charging of particles with extremely small capacitance by a discrete number of electrons.

• Received 26 March 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.807