AVS 50th International Symposium
    Surface Science Thursday Sessions
       Session SS+OM-ThA

Paper SS+OM-ThA7
Mechanism of Nanomolecular Motion Induced by Polarity Change of the Electric Field in the Self-Assembled Monolayers

Thursday, November 6, 2003, 4:00 pm, Room 327

Session: Self-Assembled Monolayers
Presenter: T. Ishida, AIST, Japan
Authors: T. Ishida, AIST, Japan
H. Fukushima, TPRC, SEIKO EPSON Corporation, Japan
T. Tamaki, AIST, Japan
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We have successfully observed the nanoscale molecular motion induced by polarity change of the electric field by STM, when small amounts of asymmetrical disulfides containing mobile terphenyl moieties were embedded into pre-assembled dodecanethiol SAMs.@footnote 1@ Taking the direction of the dipole moment into account, the thickness of embedded molecular protrusions became larger at the positive bias.@footnote 2@ However, STM experiments revealed that the thickness of the molecular protrusions was larger at the negative bias, contrary to this prediction. STS revealed the higher rectification property at the area of the terphenyl terminated monolayer where also showed the higher electrical conduction at the negative tip bias compared to positive one. The higher electrical conduction at the negative tip bias was likely to retract the STM tip, showing the apparent nanomolecular motion by the polarity change. Next, we investigated the relationship between the higher rectification property and real conformational change. When symmetric disulfide which is not easy to change molecular conformation are embedded into pre-assembled dodecanethiol SAMs for the comparison, both the rectification property and apparent molecular motion were not observed. In addition, when the STM tip was directly attached to asymmetric disulfides, rectification property was not observed in STS. Thus, we concluded that the conformational change is the influential factor to induce the higher rectification property. @FootnoteText@@footnote 1@ T. Ishida, H. Fukushima, T. Tamaki and H. Tokumoto, Jpn J. Appl. Phys. in press. @footnote 2@ H. Fukushima and T. Tamaki J. Phys. Chem. B106 7142(2002).