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Local manipulation of molecules with the optical nonlinearity just below the tips of Scanning Tunneling Microscopes

利用扫描隧道显微镜尖端下方的光学非线性对分子进行局部操纵

基本信息

批准号：
17560021
负责人：
MERA Yutaka
金额：
$ 2.24万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17560021/
关键词：
STM Optical Nonlinearity Molecule Manipulation Field Enhancement Surface Interface Properties

项目摘要

We have proposed a new method to manipulate single molecule by a light locally generated at the tunnel gap of tip and sample in a Scanning Tunneling Microscope (STM).The achievements are as follows. (1) Combining Lasers and STM, we have constructed a system of local nonlinear optical generation at the tunnel gap of tip and sample in a STM. (2) Field enhancement effects at the STM tip were estimated with FDTD method. It was found that a huge enhancement can be expected at the STM tips. (3) We have found that the optical rectifying tunneling currents due to I-V nonlinearity of STM sample tip gaps (i.e.enhancement factors) fluctuate significantly in the experiments according to the condition of tip surfaces. Extremely stable STM tips are found to be necessary to utilize the nonlinear optical generation at the STM tips. (4) Carbon nanotubes (CNT) are suitable for use as STM tips, with its remarkable electronic and mechanical properties. To investigate the field enhancement factor of CNTs by optical rectifying tunneling currents, we assessed several materials as a substrate for CNT STM observations. It was found that despite its flatness, HOPG surfaces were not suitable because of peculiar contrasts due to electronic state at the edge of graphene sheets. Au films deposited on mica were suitable substrates. (5) Reversible polymerization and depolymerization reactions of fullerene (C60) molecules are induced by tunnel injection of holes from tips of scanning tunneling microscopes similarly to the reactions induced by tunneling electrons. The bi-directional and bi-polar features of the hole-induced and electron-induced reactions can be interpreted by a unified model considering ionic reactions over symmetry-imposed barriers in the [2+2] cyclo-addition and the reverse reactions.

我们提出了一种利用扫描隧道显微镜(STM)针尖和样品隧道缝隙处局部产生的光来操纵单分子的新方法。(1)将激光与扫描隧道显微镜相结合，构建了扫描隧道显微镜针尖和样品隧道缝隙的局域非线性光学产生系统。(2)用FDTD方法估算了STM尖端的场增强效应。研究发现，在扫描隧道显微镜的尖端，可以预期会有巨大的增强。(3)在实验中，我们发现由于STM样品针尖间隙的I-V非线性引起的光学整流隧道电流(即增强因子)随针尖表面的不同而有明显的波动。发现非常稳定的STM尖端是利用STM尖端处的非线性光学产生所必需的。(4)碳纳米管(CNT)具有优异的电学和力学性能，适合用作STM针尖。为了研究光整流隧道电流对碳纳米管的场增强因子，我们评估了几种材料作为碳纳米管扫描隧道显微镜观察的衬底。研究发现，尽管石墨烯表面平坦，但由于石墨烯边缘电子态的特殊反差，HOPG表面并不适合使用。在云母上沉积Au薄膜是比较合适的衬底。(5)富勒烯(C60)分子的可逆聚合和解聚反应是由扫描隧道显微镜尖端的空穴隧道注入引起的，类似于隧道电子引起的反应。空穴诱导反应和电子诱导反应的双向和双极性特征可以用一个统一的模型来解释，该模型考虑了[2+2]环加成反应和反向反应中对称势垒上的离子反应。