title: Contact resistance in metal-molecule-metal junctions based on aliphatic SAMs: effects of surface linker and metal work function.
abstract: Using conducting probe atomic force microscopy (CP-AFM), we have formed molecular tunnel junctions consisting of alkanethiols and alkane isonitrile self-assembled monolayers sandwiched between gold, platinum, silver, and palladium contacts. We have measured the resistance of these junctions at low bias (dV/dI |V=0) as a function of alkane chain length. Extrapolation to zero chain length gives the contact resistance, R0 . R0 is strongly dependent on the type of metal used for the contacts and decreases with increasing metal work function; that is, R0,Ag > R0,Au > R0,Pd > R0,Pt. R0 is approximately 10% smaller for Au junctions with isonitrile versus thiol surface linkers. We conclude that the Fermi level of the junction lies much closer to the HOMO than to the LUMO.
authors.affiliation: Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Beebe
authors.forename: Vincent B
authors.initials: VB
authors.lastname: Engelkes
authors.forename: Larry L
authors.initials: LL
authors.lastname: Miller
authors.forename: C Daniel
authors.initials: CD
authors.lastname: Frisbie