Ito & Yokoyama Laboratory | The University of Tokyo

Recent remarkable progress on micro- or nano-fabrication technology in the semiconductor industry has been realizing ultra-high density integrated devices such as LSI. In contrast to the top-down or miniaturizing trend, the bottom-up fabrication strategy for the molecular electronics has attracted interests of many researchers. The self-assembling accumulation of functional molecules is expected to organize into molecular devices such as molecular diode and transistor in nanoscopic scale.

We have recently found that polianiline forms an inclusion complex with cyclodextrin in solution. The polyrotaxane of a conducting polymer axis and insulating cyclic molecules can be regarded as insulated molecular wire.

It is generally difficult to measure the conductivity of a single conducting polymer chain since conducting polymers tend to aggregate owing to strong attractive interaction among polymer chains. By suppressing the aggregation, the insulating cyclic molecules enable us to measure the conductivity of a single conducting polymer chain. In addition, we have established the method to measure the conductivity of a single molecular wire by fabricating the narrow-gap electrodes using the AFM lithography with Hitach Co. and applied it to various single wires such as λ?DNA, polythiophene nanofiber, and so on.

Schematic diagram of molecular transistor

AFM image of an insulated molecular wire