Solid-state nanopore fabrication in LiCl by controlled dielectric breakdown

Nanopore fabrication via the controlled dielectric breakdown (CDB) method offers an opportunity to create solid-state nanopores directly in salt solution with sub-nanometer precision. Driven by trap assisted current tunneling, the method uses localized defects, or traps, in the dielectric material to isolate a breakdown point and fabricate a single pore in less than 10 minutes. Here we present an approach to controlled dielectric breakdown of SiNx in which the nanopore is fabricated in LiCl buffer instead of the traditional KCl buffer. Direct fabrication in LiCl buffer promotes a uniform, symmetric, cylindrical nanopore structure that is fully wet and can be used for experiments in situ. We have shown that fabrication in LiCl reduces the necessity for overnight pore stabilization and allows for the desired analyte to be added in significantly less time than it would take if fabrication was performed in KCl. Pores created by this approach can be used for biosensing applications, including the detection of double-stranded DNA. DNA translocation experiments were conducted in both LiCl and KCl buffer. Experiments conducted in LiCl buffer resulted in about a 2-fold increase in dsDNA transport duration when compared to experiments conducted in KCl buffer of the same concentration. An increase in transport duration of over 10-fold in comparison to KCl was observed when the concentration of the LiCl buffer was increased by a factor of 3.