Investigation of the transport properties of PPy/[Co(EDTA)NH3Cl]•H2O nanocomposite prepared by chemical oxidation method

Charge transport across a potential barrier is important in determining the properties of many devices ranging from solar cells to the production of H-2. This paper reports the synthesis of photoadduct: [Co(EDTA)NH3Cl]center dot H2O via a photochemical route and its use as filler in polypyrrole (PPy) matrix for the formation of a semiconductor-insulator-semiconductor (SIS) nanocomposite junction by in situ chemical polymerization. Particle size of photoadduct obtained from XRD and TEM has been well correlated. TEM clearly showed a two phase system consisting of PPy flakes in between which are the photoadduct particles. This leads to the formation of an SIS junction. Thermal analysis of the nanocomposite junction revealed its higher thermal stability than pristine PPy. The dielectric constant and dielectric loss exhibit normal dispersion behavior with frequency. A decreasing trend of dielectric loss is dominated by the dc-conduction losses which is confirmed by the electric modulus formalism. From the fitted Cole-Cole impedance plot, resistance of the nanocomposite has been found to be 8 X 10(3) Omega. Different models have been used to account for the non-linear I-V curves of the synthesized SIS junction. The extended fluctuation induced tunneling (FIT) conduction model fits best, confirming the formation of an SIS junction wherein PPy flakes acts as semiconductor and the photoadduct as an insulating barrier. The shape of the insulating barrier changes upon increasing bias voltage, thereby favoring quantum mechanical tunneling. This is useful for photo-detector applications.