Contact resistance in metal-molecule-metal junctions based on aliphatic SAMs: effects of surface linker and metal work function.
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.
Beebe
Jeremy M
JM
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Engelkes
Vincent B
VB
Miller
Larry L
LL
Frisbie
C Daniel
CD