Nanogap fabrication by Joule heating of electromechanically spun suspended carbon nanofibers
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© 2017 Elsevier LtdWe present Suspended Carbon Nanofibers featuring a central nanometric gap fabricated by integration of Electro-Mechanical Spinning, pyrolysis of ultraviolet-cured microstructures and a Joule heating process. Photopatterned walls were used to suspend polymeric electrospun fibers based on a solution of SU-8. After pyrolysis, the complete structure was converted into a monolithic carbon microstructure featuring stable ohmic contact between the suspended fibers and the supporting walls without the need of further processing. By applying an electrical bias through the electrodes, the wire can be gradually thinned by excessive Joule heating, eventually forming a nanogap. The maximum supported current density in the fibers was found to be of the order of 105 A/cm2. Furthermore, the electrical characteristics of carbon nanofibers and the dimensions of the nanogaps were demonstrated to be dependent on the length of the fiber and atmosphere conditions, i.e. air or vacuum. A finite element simulation was used to gain insight into the influence of length on nanogap size. The shorter fibers modeled portrayed a significantly steeper temperature gradient, which agrees with the experimental observation of smaller gaps. The presented method facilitates an inexpensive manufacturing technique of nanogaps as small as 12 nm, holding potential for the preparation molecular electronics devices.