2004 Fiscal Year Final Research Report Summary
Single Molecule STM Nanospectroscopy using Difference Frequency Generation at the Tunnel Gap
| Project/Area Number |
14350017
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
表面界面物性
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| Research Institution | The University of Tokyo |
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Principal Investigator |
MAEDA Koji The University of Tokyo, School of Engineering, Professor, 大学院・工学系研究科, 教授 (10107443)
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| Co-Investigator(Kenkyū-buntansha) |
MERA Yutaka The University of Tokyo, School of Engineering, Research Associate, 大学院・工学系研究科, 助手 (40219960)
FUKUTANI Katsuyuki The University of Tokyo, Institute of Industrial Science, Associate Professor, 生産技術研究所, 助教授 (10228900)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Scanning Tunneling Microscopy / Infrared Absorption / Molecular Vibrations / Nonlinear Optics / Nano Resolution / Near Field / Plasmon / Micro Analysis |
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| Research Abstract |
We have developed a new scheme of single-molecule-resolved nanospectroscopy (STM-DFG) that uses an intense infrared light locally generated at the tunnel gap of tip and sample in a scanning tunneling microscope (STM). The achievements are as follows. (1)Measurements of optical field enhancement at STM probe tips : From a tunneling current arising from a rectification of optical field at the tunnel gap due to the nonlinear I-V relation, we have measured for graphite samples the optical field enhancement factors as large as 10^3 and 5×10^2 even for W tips and Pt-Ir tips, respectively. (2)Proving difference frequency generation at a tunneling gap : For the combination of C_<60> film sample and W tip that was illuminated with two laser lights from a Ti-sapphire laser (wavelength fixed) and a diode laser (wavelength swept), we have successfully acquired spectra in agreement with infrared absorption by C_<60> crystals. (3)Field enhancement effect in carbon nanotubes (CNT) : We have found a remarkable enhancement of Raman scattering from N-Dimethyl formamide (DMF) molecules only when the DMF contained CNT and the excitation light is resonant (633nm) with CNT, a signature of the expected field enhancement effect of CNT. (4)STM observations of optical field enhancement effect : Using Au nano-rods as a model sample, we have developed an STM technique to observe directly the optical enhancement taking place at individual particles by detecting the local rectified current. (5)Optimum conditions for STM-DFG : We have concluded that it is most efficient to more intensely focus the light beam, to use pulsed laser lights, to increase the set tunneling current, and to use special materials (Ag, Au, CNT) for STM tips.
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