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Investigations and Control of Electronic Properties in a Small Number of Molecules

少量分子电子特性的研究和控制

基本信息

批准号：
10305004
负责人：
MATSUSHIGE Kazumi
金额：
$ 5.57万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10305004/
关键词：
Molecular Electronics Fullerene Molecule Scanning Probe Microscopy Local Electronic Properties Non-contact Atomic Force Microscopy Kelvin Probe Force Microscopy Surface Potetial Interface Charge Transfer 単分子デバイス原子間力顕微鏡局折物性測定原子分子操作

项目摘要

The surface structures and the electronic properties of monolayer films of methyl-substituted oligothiophene pentamer (DM5T) were investigated using atomic force microscopy (AFM) with an electrically conducting probe. The films were prepared by vacuum deposition onto a metal substrate. AFM observation revealed that the molecules were arranged with their molecular axes perpendicular to the substrate. The local current vs. voltage curves obtained on the film were nonlinear and nonsymmetric with respect to the polarity of the voltage. The resistivity of the film was about 100Ωcm, which was smaller than one hundredth of that in the bulk material. It is noteworthy that the local electrical conduction is much better compared to the case of the bulk experiment. In addition, the surface potential was measured by Kelivin force microscopy (KFM). The film had a higher potential than the Pt substrate, which indicated the existence of either charge transfer from the film to the substrate or induced dipoles toward the film surface.Self-assembled monolayers (SAMs) of the thiol molecules were also investigated by scanning tunneling microscopy (STM) High-resolution imaging of octanethiol SAMs in ultrahigh vacuum environment revealed that the molecules were hexagonally packed on Au (111) surface and that the ィイD83ィエD8xィイD83ィエD8and c (4x2) reconstructed structures were formed. On the other hand, octanedithiol molecules having thiol groups at both ends were arranged eptaxially with their molecular axes parallel to the substrate. Furthermore, local I/V measurements using STM showed that the I/V curves on the octanethiol SAMs were non-linear. The conductivity was higher when the sample was posively biased while the I/V characteristics of the octanedithiol SAMs exhibited a symmetric feature. The results suggested that the current was affected by the local electric field by the molecular dipole.

利用原子力显微镜（AFM）研究了甲基取代的噻吩五聚体（DM 5 T）单层膜的表面结构和电子性质。通过真空沉积在金属基底上制备膜。原子力显微镜观察发现，分子排列与其分子轴垂直于衬底。在膜上获得的局部电流-电压曲线是非线性的，并且相对于电压的极性是非对称的。薄膜的电阻率约为100Ωcm，小于体材料的百分之一。值得注意的是，与体实验的情况相比，局部导电要好得多。此外，通过Kelivin力显微镜（KFM）测量表面电位。该膜具有比Pt基底更高的电势，用扫描隧道显微镜（STM）研究了硫醇分子的自组装单分子膜（SAMs）。高分辨扫描电子显微镜（SEM）研究表明，硫醇分子在Au（111）表面呈六角堆积。表面形成了C_（83）C_（83）D_（83）C_（83）D_（83）C_（83）和C_（4x 2）重构结构。另一方面，在两端具有硫醇基团的辛烷二硫醇分子以其分子轴平行于基底的方式epaxially排列。此外，使用STM的局部I/V测量表明，在辛烷乙磺酸自组装膜上的I/V曲线是非线性的。当样品被正偏压时，电导率较高，而辛二硫醇自组装膜的I/V特性表现出对称特征。结果表明，分子偶极产生的局域电场对电流有一定的影响。