The smooth Coulomb blockade (CB) I-V curve is sometimes observed in cryogenic scanning tunneling microscopy using a voltage biased tip to scan a metal film. Our experiments always give some evidence of the Coulomb staircase, characteristic of two tunnel capacitors in series (STM tip, small particle, and substrate) accompanying the smooth CB I-V curves. We suggest that a small (100 Å) particle occasionally encountered between tip and surface, providing a capacitance of order 10-18 F unaffected by voltage biased leads, is the origin of both effects.
ASJC Scopus subject areas
- General Physics and Astronomy