Influence of the counter ion on the properties of poly(o-toluidine) thin films and their Schottky diodes

The influence of various counter ions on the electrochemical, morphological and optical properties of poly(o-toluidine) (POT) thin films and on the electrical properties of POT-based diodes was investigated. The POT thin films were deposited on indium tin oxide (ITO)-coated glass substrates by electrochemical polymerization under cyclic voltammetric conditions from o-toluidine monomer in aqueous solutions of HCl, H2SO4 and HNO3. The deposited films were characterized by cyclic voltammetry, scanning electron microscopy and UV–vis spectrophotometry. It was observed that the current densities and optical absorption spectra are influenced by the counter ions of the electrolyte solutions.On the other hand, ITO/POT/Al devices were fabricated by thermal evaporation of aluminum circular electrodes on the as-deposited POT films. The current–voltage (C–V) characteristics of these devices are non linear. The diode parameters were calculated from current–voltage (I–V) characteristics using the modified Shockley equation. The C–V and capacitance–frequency (C–F) characteristics were also measured. These measurements revealed that the junction electrical parameters depend strongly on the type of supporting electrolytes used in the synthesis of the polymer.