Characterization of the tip-loading force-dependent tunneling behavior in alkanethiol metal-molecule-metal junctions by conducting atomic force microscopy

We report on a tip-loading force-dependent tunneling behavior through alkanethiol self-assembled monolayers formed in metal-molecule-metal junctions, using conducting atomic force microscopy. The metal-molecule contacts were formed by placing a conductive tip in a stationary point contact on alkanethiol self-assembled monolayers under a controlled tip-loading force. Current-voltage characteristics in the alkanethiol junctions are simultaneously measured, while varying the loading forces. Tunneling current through the alkanethiol junctions increases and decay coefficient beta(N) decreases, respectively, with increasing tip-loading force, which results from enhanced intermolecular charge transfer in a tilted molecular configuration Under the tip-loading effect. (C) 2008 Elsevier B.V. All rights reserved.