Electromigration Current Rectification In a Single Cylindrical Nanopore

We present the experimental measurements of electromigration current through a single cylindrical nanopores. A cylindrical nanopore with ~175 nm diameter was fabricated using standard clean-room semiconductor processing techniques. The fabricated nanopore exhibits electromigration rectification with low concentration solutions (100 μM KCl) and nearly symmetric conductance with in stronger ionic strength solutions (100 mM KCl) . Our results show that the rectification is consistent with the two distinct electromigration regimes: (1) Ohmic regime where the electric double layers are thin compared to the pore size (κa>1) and (2) thick or overlapping electric double layers (κa<1) where the conductance of the nanopore is strongly influenced by the surface conductance in the EDL. Thick EDL's (κa<1) exhibit current rectification due to concentration polarization while thinner EDLs show nearly symmetric conductance.