High quality nanogap electrodes for electronic transport measurements of single molecules

Electromigrated nanogaps have frequently been used in molecular scale electronics. We use a computer controlled electromigration (CCE) process for creating nanogaps at room temperature permitting characterization of bare gaps prior to application of molecules. This is very different from other approaches where nanogaps are formed by a simple voltage ramp performed at low temperature with molecules already attached to the nanowire. Using CCE, we formed nanogaps at room temperature on both thick substrates and thin SiN_x membranes compatible with transmission electron microscopy. We showed that the electromigration process evolves through an initial bulk behavior regime and crosses over to a ballistic conduction regime. It was found that nanogaps formed on SiN_x membranes are clean of parasitic conduction pathways and contamination. This work has implications to the design of clean metallic electrodes for use in nanoscale devices.