| Co-Investigator(Kenkyū-buntansha) |
OHTA Toshiaki School of Science, Dept.of Chemistry, The University of Tokyo Professor, 大学院・理学系研究科, 教授 (80011675)
YOKOYAMA Toshihiko School of Science, Dept.of Chemistry, The University of Tokyo Associate Professor, 大学院・理学系研究科, 助教授 (20200917)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2000: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1999: ¥3,300,000 (Direct Cost: ¥3,300,000)
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| Research Abstract |
The purpose of this research proposal is to understand microscopic mechanism of molecular self-assembly via. investigating formation process of self-assembled monolayers of thiol and related molecules by the use of STM and XAFS.In particular, we have been focusing on effects of molecule-substrate interactions on the self-assembly. The molecular orientation and the interface structure during self-assembling process have been investigated for different substrates (Au, Ag, Cu, O/Cu, Si). From systematic comparison for these substrates, we found three important factors to form well-ordered structures ; (1) sufficient molecular density, (2) surface diffusion and (3) consistency between intralayer and interface structures. It needs for achieving a well-ordered structure to satisfy all the three factors. We also found that the adsorption process is the rate-limiting step if the factor (1) is relatively important compared to the other factors while the diffusion process is the rate-limiting on
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e if the factor (2) is crucial. Another focusing point is effects of change in intermolecular interactions when introducing functional groups to the end of the alkanethiol molecules. Particularly, we have investigated self-assembly of thiophene- and porphyrin-introduced alkanethiols on gold substrates. In case of thiophene-introduced one, since the structure consistency as mentioned as factor (3) changes depending on molecular density, the self-assembly was found to take place only for a certain coverage range. In case of porphyrin-introduced molecules they exhibit no self-assembly unless the thiol group is spatially separated from the porphyrin moiety via.inserting long alkyl chains, because the large porphyrin moiety prevents the thiol group from having access to the substrate due to steric hindrance, which results in lower molecular density. Furthermore, we have investigated self-assembly of chalcogenophenes, of which structures are totally different from thiol, and found that selenophene (C_4H_4Se) forms a highly-ordered structure. Less
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