BFabrication and characterization of nanopore-based electrodes with radii down to 2 nm

We report on the fabrication and characterization of gold nanoelectrodes with carefully controlled nanometer dimensions in a matrix of insulating silicon nitride. A focused electron beam was employed to drill nanopores in a thin silicon nitride membrane. The size and shape of the nanopores were studied with high-resolution transmission electron microscopy and electron-energy-loss two-dimensional maps. The pores were subsequently filled with gold, yielding conically shaped nanoelectrodes. The nanoelectrodes were examined by atomic and electrostatic force microscopy. Their applicability in electrochemistry was demonstrated by steady-state cyclic voltammetry. Pores with a radii down to 0.4 nm and electrodes with radii down to 2 nm are demonstrated. The ability to fabricate electrodes of accurately controlled nanometer dimensions is a key element in several areas of nanoscience, including molecular electronics and nanoelec-trochemistry. Point contacts have been used widely in quantum transport studies1,2 and to probe electrical conduc-tion through a limited number of molecules down to the single-molecule level.3-6 In the context of electrochemistry, the main fundamental interest in these devices lies in thei