Nanometer-scale gaps between metallic electrodes fabricated using a statistical alignment technique

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Abstract
We describe a fabrication process for the creation of nanoscale gaps between metallic electrodes based on a statistical alignment method. This technique is appropriate for applications in which a sparse array of gaps, connected to macroscopic electrodes and pads, is required, for example the study of single molecule electrical conduction. This process relies on aligning two separate levels of electron beam lithography defining opposing arrays of metallic wires, so that the gap may be defined between wires of two dissimilar materials, such as nickel and gold. Lithographic definition of gaps small enough to permit tunneling was reliable and had high yield. Fitting an analytical model of tunnel conductance to measured electrical characteristics of a typical gap demonstrates a gap spacing of 1.3±0.7nm. The process is compatible with most conventional electron-beam lithography systems and does not require the use of unusually high resolution or accurate pattern placement.