2013 Volume 52 Issue 1 Pages 19-25
Molecular devices have attracted growing interest as a potential candidate for future nanoscale devices. Electrical characterization of a single molecule bridging between metal electrodes is essential for the realization of molecular devices and requires the fabrication of nanogap electrodes whose gap widths are few nanometers. In this paper, we review representative methods for fabricating nanogap electrodes and report our developed methods using focused ion beams (FIBs). The presented method is based on in situ monitoring of etching steps by measuring current through patterned electrodes and on electronic termination of etching steps just after nanogap formation. By using this method, electrode gaps much narrower than the FIB spot size can be reproducibly fabricated. The minimum gap width achieved is ∼3nm, and the fabrication yield reached ∼90% for 3-6nm wide gaps. The fabricated nanogap electrodes show high insulating resistance ranging from 10GΩ to 1TΩ.
