Single-electron tunneling up to room temperature

Ultrasmall (< 5nm in lateral diameter) double-barrier tunnel junctions have been realized using metal particles (2-5 nm in diameter) sandwiched in between a metallic substrate and the metallic tip of a scanning tunneling microscope (STM). The particles were either grown by e-beam evaporation or prepared using colloid chemistry. Two electrical transport effects, in good agreement with the semi-classical theory of single-electron tunneling, have been found at room temperature: the Coulomb gap and the Coulomb staircase. The interpretation in terms of single-electron tunneling is further supported by liquid Helium temperature STM measurements on identical samples.