Conductivity Measurements of Stilbene-Based Molecules Incorporated into Self-Assembled Monolayers by Conducting Probe Atomic Force Microscopy

Abstract

We describe a technique for acquiring current-voltage (I–V) characteristics of a metal-molecule-metal junction using a conducting probe atomic force microscopy (CP-AFM) technique. To conduct a repetitive experiment efficiently, we have utilized the current imaging tunneling spectroscopy (CITS) mode of the CP-AFM system. We have prepared a self-assembled monolayer of 1-decanethiol on Au(111) substrate where 4,4'-bis(mercaptomethyl)-trans-stilbene (BMMS) molecules have been incorporated. We demonstrate that we have constructed a conductivity map derived from a set of CITS data. Conductance peaks presumably involved by BMMS molecules have been found in the conductivity map and the corresponding I–V curves have exhibited fluctuations in current. The causes of the current fluctuations are also discussed.

Fabrication of Steady Junctions Consisting of α,ω-Bis(thioacetate) Oligo(p-phenylene vinylene)s in Nanogap Electrodes

“…For the realization of molecular devices with metal−molecule−metal junctions containing functional molecules, a number of studies have been conducted previous to this study. − In particular, studies on potential “molecular nanowires” based on dithiol terminated π-conjugated oligomers is proceeding at a rapid pace. Typical Au−nanowire−Au junctions formed with oligo(phenylene vinylene) (OPV), − oligo(phenylene ethynylene) (OPE), − ,− oligo(phenylene) (OP), , and oligo(thiophene) (OT), − have been reported. Since the OPV backbone consists of a higher degree of planarity, and thus better π-conjugation, than those for OPE or the other molecules, ,− Au−OPV−Au junctions always show higher electronic conductance than other conjugated oligomers. − For example, Blum et al showed that the resistance of a cross-wire tunneling junction consisting of self-assembled monolayers (SAMs) of OPV with butoxy side-chain molecules was estimated to be 0.5 ± 0.2 MΩ .…”

“…[1][2][3][4] In particular, studies on potential ''molecular nanowires" based on dithiol terminated π-conjugated oligomers is proceeding at a rapid pace. Typical Au-nanowire-Au junctions formed with oligo(phenylene vinylene) (OPV), [5][6][7][8][9][10][11] oligo(phenylene ethy-nylene) (OPE), [5][6][7][8][9][12][13][14][15][16][17] oligo(phenylene) (OP), 18,19 and oligo-(thiophene) (OT), [20][21][22] have been reported. Since the OPV backbone consists of a higher degree of planarity, and thus better π-conjugation, than those for OPE or the other molecules, 9,[23][24] Au-OPV-Au junctions always show higher electronic conductance than other conjugated oligomers.…”

Refinement of conditions of point-contact current imaging atomic force microscopy for molecular-scale conduction measurements

“…By this change, the quality of the measured data was obviously improved from the previous results. If the interaction between the cantilever and sample is too strong for them to disconnect, for example, due to the presence of a sticky material, the cantilever can be retracted by a displacement large enough to disconnect the sample and the cantilever once and then returned to the original position [10].…”