title: Chemical fabrication of heterometallic nanogaps for molecular transport junctions.
abstract: We report a simple and reproducible method for fabricating heterometallic nanogaps, which are made of two different metal nanorods separated by a nanometer-sized gap. The method is based upon on-wire lithography, which is a chemically enabled technique used to synthesize a wide variety of nanowire-based structures (e.g., nanogaps and disk arrays). This method can be used to fabricate pairs of metallic electrodes, which exhibit distinct work functions and are separated by gaps as small as 2 nm. Furthermore, we demonstrate that a symmetric thiol-terminated molecule can be assembled into such heterometallic nanogaps to form molecular transport junctions (MTJs) that exhibit molecular diode behavior. Theoretical calculations demonstrate that the coupling strength between gold and sulfur (Au-S) is 2.5 times stronger than that of Pt-S. In addition, the structures form Raman hot spots in the gap, allowing the spectroscopic characterization of the molecules that make up the MTJs.
authors.affiliation: Department of Chemistry and International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Chen
authors.forename: Sina
authors.initials: S
authors.lastname: Yeganeh
authors.forename: Lidong
authors.initials: L
authors.lastname: Qin
authors.forename: Shuzhou
authors.initials: S
authors.lastname: Li
authors.forename: Can
authors.initials: C
authors.lastname: Xue
authors.forename: Adam B
authors.initials: AB
authors.lastname: Braunschweig
authors.forename: George C
authors.initials: GC
authors.lastname: Schatz
authors.forename: Mark A
authors.initials: MA
authors.lastname: Ratner
authors.forename: Chad A
authors.initials: CA
authors.lastname: Mirkin
mesh_terms: D003460:Crystallization / Q000379:methods; D004553:Electric Conductivity; D004563:Electrochemistry / Q000379:methods; D004579:Electron Transport; D006046:Gold / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008839:Microelectrodes; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D010984:Platinum / Q000737:chemistry*; D012666:Semiconductors; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances; D010984:Platinum; D006046:Gold