Solution processable sol–gel derived titania gate dielectric for organic field effect transistors

Abstract

A gate dielectric has key role in thin film transistors. Insulating polymers incorporated with oxide nanoparticles are the ideal candidates for the gate dielectrics due to their solution processability and relatively high dielectric constant. The polyvinyl alcohol cross linked with ammonium dichromate was spun onto fluorine doped tin oxide (FTO) substrates. Titania particles were incorporated into a mixture of ammonium dichromate and polyvinyl alcohol (PVAad) solution and the resultant films were irradiated by ultraviolet irradiation. TiO2 particles were prepared using acetic acid as a surfactant by sol–gel method. Metal–insulator–semiconductor (FTO/(PVAad + TiO2)/Au) structure was fabricated by evaporating Au electrode. The electrical properties of polymer composites layer have been studied with the effect of binding agent, concentration of TiO2 nanoparticles, and the irradiation of UV light. Capacitance–voltage, capacitance–frequency, and current–voltage measurements were performed using two probes measurement setup. The obtained electrical results illustrated that the dielectric constant of prepared films was increased from approximately 2 for PVAad to 7 for PVAad +TiO2 films. These results further corroborated that the capacitance is independent of frequency and the leakage current was less than 2 × 10−12 A. This leakage current is small enough and hence PVAad + TiO2 is an ideal gate dielectric for the fabrication of field effect transistors. The surface morphology of composite films has been studied by means of field emission scanning electron microscopy. The micrograph images illustrated huge variation in the morphologies of the hybrid films after incorporation titania particles into polymer matrix and UV irradiation.