Electromechanical properties of self-assembled monolayers of tetrathiafulvalene derivatives studied by conducting probe atomic force microscopy

The electrical conduction of metal-molecule-metal junctions formed between Au-supported selfassembled 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. © 2010 American Chemical Society