Surface Polymerization of the Thiophen Molecules in Chemically Adsorbed Monolayer
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1091-AA07-41
Surface Polymerization of the Thiophen Molecules in Chemically Adsorbed Monolayer Shin-ichi Yamamoto1, and Kazufumi Ogawa2 1
Department of Electrical Engineering, Kobe City College of Technology, 8-3, GakuenHigashi-machi, Nishi-ku, Kobe City, 651-2194, Japan 2
Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20, Hayashi-cho, Takamatsu, 761-0396, Japan Abstract We have observed the assembly of a chemically adsorbed monomolecularlayer (CAM) into microwires, connections, and an electric path according to the location within field regions of a lithographically patterned array of two platinum (Pt) electrodes. A Pt electrode/monolayer/Pt electrode junction was fabricated by the self-assembly of a rigid monomolecular, namely 3-{6-{11-(Trichlorosilyl) undecanoyl} hexyl} thiophene (TEN) with thiophen groups, in the lateral direction between the Pt gap electrodes. The technique of a conductive probe AFM (CP-AFM) has been used to investigate the forward bias conduction properties of a TEN film grown by a wet process deposition on a glass substrate. The self-assembly depends on: (1) the ideal rigidity of the chemically adsorptive monomolecular layer (CAM) and (2) the strong affinity of the thiophen end groups of the CAM for the Pt electrode. The current–voltage (I–V) characteristics of the conjugated thiophen junction exhibited stepwise features at room temperature. From the results in the atmosphere, the conductivity of a lateral conjugated polythiophen group was calculated to be 5.0×104 S/cm. 1. Introduction The conductive probe AFM (CP-AFM) also seems to be a powerful method for investigating the current-voltage (I–V) characteristics of a metal–molecule–metal probe junction [1]. In these methods, the preparation of a sample where molecules of interest are fixed in a controlled manner is very important. For example, Leatherman et al. prepared such SAMs where thiolderivatized carotene molecules are sparsely dispersed in SAMs of 1-docosanethiol [1]. Cui et al. inserted 1,8-octanedithiol in a matrix SAM of 1-octanethiol [2]. In the latter paper, they conducted I–V measurements on the sample to evaluate the single-molecule conductivity [2]. Although such repetitive measurements were necessary for statistical analysis of the single-molecule conductivity, it has not been carried out to measure the current value in the lateral direction. The metal-molecular-metal is of both fundamental and technological interest, and is
useful for exploring the structural and electronic factors affecting electrical transport in molecules [3]. In this field, impressive progress has been made on carbon nanotubes,[4] deoxyribonucleic acid [5] and low molecular weight materials (e.g.,dithiols, conjugated phenylene ethynylene oligomers, etc.) [6]. However, few reports have dealt with the fabrication of nanojunctions by using conjugated polymers (excluding oligomers), [7] although the outstanding electronic–photonic properties of conjugated polymers have been well known since the 1990’s [8]. The f
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