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RESEARCH PRODUCT

Electrochemical fabrication of metal/oxide/conducting polymer junction

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After discovery of conducting polymers and the possibility to modify their electrical properties from insulating to metallic like behavior by doping and a careful choice of the processing conditions, a large amount of research effort has been devoted to the theoretical understanding of their solid state properties as well as to exploit the possible application of conducting polymers in many technological fields including large area organic electronics, polymer photovoltaic cell, and sensors. 1-4 Organic thin film transistors appear very promising devices for the development of low cost, flexible, and disposable plastic electronics. In order to reduce the operating voltage it has been suggested in the literature to use mixed inorganic–organic thin film transistors by assembling a structure formed by metal bottom contact/dielectric layer gate/organic semiconductor/top contact source/drain. According to this, a wet electrochemical route appears to be very promising in terms of cost, at least for the preparation of thin thickness 10 nm or thick thickness 10 nm oxide films by anodizing in aqueous electrolytes. Moreover, by taking into account the possibility to grow semiconducting polymers on wide bandgap dielectric oxide Ta2O5 by a photoelectrochemical route, which has been shown recently, 5,6 it seems very appealing to exploit an integral electrochemical route to fabricate advanced inorganic/organic hybrid structure which could be used as a building block for a field effect transistor FET junction. In this paper, we describe and discuss the electrochemical fabrication of a hybrid structure to be used in the production of an inorganic–organic field effect transistor IOFET using 3,4polyethylenedioxythiophene PEDOT as a semiconducting polymer and anodic films grown on the Ti-10 atom % Zr alloy as dielectrics. The choice of the oxide is based on its low dark current value and quite high photocurrent intensity, under monochromatic light, at not too high anodic potential and photon energy, 7 as well as on its high dielectric permittivity 45, according to Ref. 8. The metal/oxide/ polymer junctions are investigated by photocurrent spectroscopy PCS and scanning electron microscopy SEM. Finally, output transistor characteristics are recorded in order to test the performance of the junctions in the IOFET structure. Experimental Ti-10 atom % Zr alloys were prepared by dc magnetron sputtering. Targets consisted of 99.9% zirconium disk, of 100 mm diameter, with an appropriate number of 99.9% titanium disks, of 20 mm diameter, located symmetrically on the erosion region for the preparation of the alloys. Substrates used were glass plates. 8 The composition of the alloy was determined by Rutherford backscattering