Electrochemical Fabrication of Inorganic/Organic Field Effect Transistor

After discovery of conducting polymers and the possibility to modify their electrical properties (from insulating to metallic-like behaviour) 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 (1-2). Organic thin-film transistors appears very promising for the development of low cost, flexible and disposable plastic electronics. In order to reduce the operating voltage it has been suggested in literature the use of mixed organic-inorganic thin film transistors by assembling a structure formed by: metal (bottom contact)/ dielectric layer (gate)/organic semiconductor/top contact (source/drain). According to this, we have successfully exploited the possibility to grow photoelectrochemically on a wide band gap oxide dielectric (Ta2O5) conducting polymers, which are known to underway an electrical transition from metallic to semiconducting state under suitable polarization into solution (polypyrrole) (3). Starting from these results, in this work we describe and discuss the electrochemical fabrication of Inorganic Organic Field Effect Transistor using 3-4 polyethylene dioxythiophene (PEDOT) as conducting polymer and anodic films on Ti-10at.%Zr alloy as dielectrics, due to their high dielectric constant and low leakage current (4). The fabricated metal/oxide/polymer junctions are characterized by photocurrent spectroscopy (PCS) and scanning electron microscopy (SEM). Finally, output transistoric characteristic are recorded in order to test the performance of the junctions as IOFET.