title: Directly addressable sub-3 nm gold nanogaps fabricated by Nanoskiving using self-assembled monolayers as templates.
abstract: This paper describes the fabrication of electrically addressable, high-aspect-ratio (>10000:1) nanowires of gold with square cross sections of 100 nm on each side that are separated by gaps of 1.7-2.2 nm which were defined using self-assembled monolayers (SAMs) as templates. We fabricated these nanowires and nanogaps without a clean room or any photo- or electron-beam lithographic processes by mechanically sectioning sandwich structures of gold separated by a SAM using an ultramicrotome. This process is a form of edge lithography known as Nanoskiving. These wires can be manually positioned by transporting them on drops of water and are directly electrically addressable; no further lithography is required to connect them to an electrometer. Once a block has been prepared for Nanoskiving (which takes less than one day), hundreds of thousands of nanogaps can be generated, on demand, at a rate of about one nanogap per second. After ashing the organic components with oxygen plasma, we measured the width of a free-standing gap formed from a SAM of 16-mercaptodohexanoic acid (2.4 nm in length) of 2.6 ± 0.5 nm by transmission electron microscopy. By fitting current-voltage plots of unashed gaps containing three alkanedithiolates of differing lengths to Simmons’ approximation, we derived a value of β = 0.75 Å(-1) (0.94 n(C)(-1)) at 500 mV. This value is in excellent agreement with literature values determined by a variety of methods, demonstrating that the gap-size can be controlled at resolutions as low as 2.5 Å (i.e., two carbon atoms).
authors.affiliation: Stratingh Institute for Chemistry, and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Parisa
authors.initials: P
authors.lastname: Pourhossein
authors.forename: Ryan C
authors.initials: RC
authors.lastname: Chiechi
mesh_terms: D004553:Electric Conductivity; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006046:Gold / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008839:Microelectrodes; D008968:Molecular Conformation; D054802:Molecular Imprinting / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000295:instrumentation*; D010316:Particle Size; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances; D006046:Gold