The surface characterization of molecular interaction was investigated by measuring the properties of chemically adsorbed monolayers (CAMs) attached to the glass substrate in the lateral direction. Atomic Force Microscopy (AFM) with current mode and the interdigitated electrodes has been used for surface characterization of Thiophen Molecules by electro-oxidative polymerization. We formed TEN of polylthiophen groups with Pt-patterned electrodes on glass surfaces and measured the conductance under small bias voltage with a conductive cantilever. We could detect current through the TEN of CAMs in the vicinity of the electrodes about 100 um from the edge of the Pt electrode in the air. The conductivity of the TEN of CAMS measured using the glass substrates with interdigitated (comb) electrodes (electrodes gap are 200 um) was not dependent on the humidity. From the results in a nitrogen atmosphere, the resistivity of CAMs of polythiophen without any dopant in a lateral direction was ohmically estimated to be at least 1E3 s/cm.
A long chain molecule, TEN having a Thiophen group at the molecular end, a trichlorosilyl group at the other end, and an ester group in the middle, was synthesized. The thiophen group, trichlorosilyl group, and ester group were introduced for preparing conjugated bonds via electro-oxidative polymerization, chemical adsorption to a substrate having an active hydrogen such as a hydroxyl group (-OH), and by increasing the flexibility of the molecule at the electro-oxidative polymerization, respectively.
In this study, we formed monomolecular layers of TEN on metal-patterned glass substrates by an electro-oxidizative polymerization technique, and measured the electrical conductivity of the conjugated bond of TEN in the lateral direction by atomic force microscopy (AFM) with a conductive cantilever as a counter electrode. We also carried out macroscopic measurements of the conductivity of Chemically adsorbed monolayer (CAM) under controlled atmosphere using samples made on substrates with interdigitated (comb) electrodes, and compared the results with the microscopic measurement by conductive AFM.
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