PHYSICAL PROPERTY OF MOLECULARJ3EVICE CONNECTED WITH INSULATED MOLECULAR WIRES

用环糊精（CDs）和导电聚合物聚苯胺（PANI）合成的分子纳米管形成了一种新型分子线，并利用原子力显微镜（AFM）观察了这种绝缘分子线的结构。这种包合物可以看作是绝缘的分子线，因为导电聚合物被CD分子作为绝缘体覆盖。在这项研究中，我们的目标是制作一种分子器件，使用单个绝缘分子线作为材料连接外部电极。对于由绝缘分子线连接的分子器件，我们成功地用AFM光刻技术制作了两个电极（电极之间的间隙约为500 nm）的SiO_2衬底。首先，我们在衬底上沉积了碳纳米管作为电极之间的桥梁，并测量了两个电极之间的电阻率，以确定电极衬底的质量。结果表明，测得的ca. 100 kΩ的电阻率主要归因于电极与碳纳米管之间的接触电阻率。虽然我们现在尝试沉积绝缘分子线来弥合电极之间的间隙，但在该系统中，如果绝缘分子线的电阻率小于接触电阻率，则很难高精度地测量分子的固有电导率。因此，我们计划在聚苯胺的两端添加硫醇以使其与电极良好接触。由于掺杂的绝缘分子线具有较高的导电性，可以作为分子器件的理想分子线。

We have recently found a novel kind of molecular wire formed by the molecular nanotube synthesized from cyclodextrins (CDs) and a conducting polymer, polyaniline (PANI), and observed the structure of the insulated molecular wire by atomic force microscopy (AFM). This inclusion complex can be regarded as insulated molecular wire, because a conducting polymer is covered by CD molecules as insulator. In this study, we aim to make a molecular device using a single insulated molecular wire as a material for the connection between the external electrodes.For a molecular device connected by the insulated molecular wire, we have successfully made SiO_2 substrates with two electrodes (the gap bewtween electrodes is ca. 500 nm) by AFM lithography. Firstly, we deposited the carbon nanotube to bridge the gap between electrodes on the substrate and measured the resistivity between two electrodes to confirm the quality of the substrate with electrodes. It was found that the resistivity of ca. 100 kΩ measured was dominantly ascribable to the contact resistivity between the electrode and the carbon nanotube. Although we now try to deposit the insulated molecular wire to bridge the gap between electrodes now, the intrinsic conductivity of the molecule is difficult to measure with high accuracy in this system if the resistivity of the insulated molecular wire is smaller than the contact resistivity. Thus, we plan to synthesize PANI with thiol at the both ends to contact well to electrodes.Since it is expected that the doped insulated molecular wire had high conductivity, it can be great candidate of the molecular wire for the molecular device.