Fabrication and Evaluation of Nanoscale Quantum Structure Using Functional Organic Molecules

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The aim of this research is to construct one-dimensional molecular wires, especially, conducting nanowires, and to control their patterns on the solid surface, consequently, fabricating single-electron tunneling device with organic molecules. In addition, independently-driven double-tip scanning tunneling microscope (WT-STM), which is a novel system to evaluate functionalities of such nanoscale structures, is newly constructed.This year, we investigated the two-dimensionally ordered structures of two component molecular monolayers, in which the molecules of diacetylene compounds and fatty acid lay parallel to the surface on the underlying HOPG. The possibility of obtaining the microscopically mixed regions varied depending on the ratio of the relative lengths of the two molecules. Poly-diacetylene molecular wires can be successfully fabricated at intended positions on the surface using chain polymerization by applying pulsed bias voltage from the STM tip.We have evaluated the conductivity of ultrathin molecular sheet of diacetylene compounds using WT-STM. We made the sample of six layers with poly-diacetylene compounds by LB method and irradiation of UV light. The distances of the two tips were varied from sub-micron to hundreds microns. Obtained results showed a significantly high conductivity of its film compared with that of the bulk structure. It is considered that electronic feature of one-dimensional and microscopic structures of molecular systems are quite different from that of three dimensional and macroscopic, that is, bulk molecular system. And this result is quite promising for the constructions of nanoscale molecular-based devices with various noble functions.