Electromechanical Properties of Self-Assembled Monolayers of Tetrathiafulvalene Derivatives Studied by Conducting Probe Atomic Force Microscopy

Abstract

The electrical conduction of metal−molecule−metal junctions formed between Au-supported self-assembled monolayers (SAMs) of symmetric tetrathiafulvalene (TTF) derivatives and a Pt-coated atomic force microscope (AFM) tip has been measured under different compression forces using conducting probe AFM. The TTFs are linked to the metal through double metal−thiol linkers on both sides of the molecule. The TTF junctions exhibit remarkably high electrical conduction with estimated single molecule resistance of 14.7 ± 3.4 GΩ, corresponding to the molecular resistivity of 390 Ω·cm. A single molecule resistance of a comparable length 1-decanethiol molecule is estimated to be several orders of magnitude higher with the value of 950 ± 22 GΩ. The TTF junction resistance displayed a unique nonlinear dependence with the compression force. The dependence is attributed to the change in the intermolecular electronic coupling between the TTF molecules.