Electrostatic trapping of single conducting nanoparticles between nanoelectrodes

For molecular electronics, one needs the ability to electrically address a single conducting molecule. We report on the fabrication of stable Pt electrodes with a spacing down to 4 nm and demonstrate a new deposition technique, i.e., electrostatic trapping, which can be used to bridge the electrodes in a controlled way with a single conducting nanoparticle such as a conjugated or metal-cluster molecule. In electrostatic trapping, nanoparticles are polarized by an applied electric field and are attracted to the gap between the electrodes where the field is maximum. The feasibility of electrostatic trapping is demonstrated for Pd colloids. Transport measurements on a single Pd nanoparticle show single electron tunneling coexisting with tunnel-barrier suppression.