Current-voltage characterization of doped polystyrene thin films with view to gas sensing

Abstract

Current-voltage measurements of iodine doped polystyrene thin films as a function of dopant concentration, temperature and radiation have been carried out. The thin films were prepared by solution casting method taking the constituents in right proportions. All devices showed memory arid threshold switching except for doped annealed samples that lost both memory threshold switching at a temperature of 90°(:. The thickness was varied from 3-7/lm while the concentration of iodine varied from 0.025 to 0.100 g. The threshold voltage was lower in pure samples than in doped samples indicating an increase in disorder in the arrangements of the atoms. Irradiated and annealed devices showed a marked increase in threshold voltage. Once the pure samples switched from OFF-state to ON-state they remained in the ON state but the doped samples returned to their original state after 33 minutes to 3 hours of switching depending on the concentrations. The space charge limited current theory is a suitable model to explain condition in these polymeric materials. The ON-state was ohmic while the OFF-state obeyed Child-Langmuir law.