The influence of thickness and preparation temperature of doped polypyrrole films on the electrical and chemical sensing properties of polypyrrole/gold Schottky barrier diodes

A gold contact with polypyrrole (PPy) doped with the copper phthalocyanine toluenesulfonate (CuPcTS) anion (Au/PPy-CuPcTS) was studied using complex i mpedance spectroscopy, current density voltage (J-V) and capacitance voltag e (C-V) measurements. The J-V characteristics of these junctions are asymme trical and nonlinear. The junction parameters extracted from the J-V charac teristics (the saturation current density, the rectification ratio and the ideality factor) and from the C-V characteristics (the built-in voltage and the charge carrier concentration) are strongly influenced by the thickness and by the preparation temperature of the PPy layer. These Schottky diodes show high sensitivity to NOx in the parts per million concentration range, which was explained by changes in the contact potential and in the carrier concentration of the PPy layer due to NOx exposure. The NOx sensitivity is influenced by the thickness as well as by the preparation temperature of t he PPy layer. The: junction parameters and the gas sensitivity can be impro ved largely by increasing the preparation temperature of the PPy films up t o the glass transition temperature of PPy.