Single-electron tunnelling observed at room temperature by scanning-tunnelling microscopy

Ultrasmall (< or approx.5 nm in lateral diameter) double-barrier tunnel junctions have been realized using a scanning tunnelling microscope, and an optimized metal particle-oxide-metallic substrate system. Three electrical transport effects, all in good agreement with the semi-classical theory of single-electron tunnelling, have been found at room temperature: the Coulomb gap, the Coulomb staircase and zero-bias conductance oscillations as a function of tip-particle distance. (orig.)