Atomic Scale Conductance Induced by Single Impurity Charging

Abstract

A scanning tunneling microscope was used to probe electron transport through an alkali doped ${\mathrm{C}}_{60}$ monolayer crystal on ${\mathrm{A}\mathrm{l}}_2{\mathrm{O}}_3$ grown by the oxidation of NiAl(110). Each individual alkali atom forms a localized complex with the neighboring ${\mathrm{C}}_{60}$ molecules. Charging of the complex induces a substantial rise in the current that persists outside the physical dimensions of the complex. This induction of the current rise is characterized by spatially resolved spectroscopy and mapping of the differential conductance ($dI/dV$) in the vicinity of the complex.