Contact resistance in metal-molecule-metal junctions based on aliphatic SAMs: effects of surface linker and metal work function

Jeremy M Beebe; Vincent B Engelkes; Larry L Miller; C Daniel Frisbie

doi:10.1021/ja0268332

Contact resistance in metal-molecule-metal junctions based on aliphatic SAMs: effects of surface linker and metal work function

J Am Chem Soc. 2002 Sep 25;124(38):11268-9. doi: 10.1021/ja0268332.

Authors

Jeremy M Beebe¹, Vincent B Engelkes, Larry L Miller, C Daniel Frisbie

Affiliation

¹ Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.

PMID: 12236731
DOI: 10.1021/ja0268332

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.