Electrical and NOx gas sensing properties of metallophthalocyanine-doped polypyrrole/silicon heterojunctions

Abstract Heterojunctions between silicon and polypyrrole (PPy) doped with metal phthalocyanine toluenesulfonate (MPcTS) anions have been studied using current–voltage and capacitance–voltage measurements. The results from current–voltage measurements at different temperatures indicated that in the temperature range close to room temperature the thermionic emission current is dominant. These heterojunctions are sensitive to NO x in the ppm concentration range. The electrical and gas sensing properties are strongly influenced by both the PPy characteristics (dopant, film thickness, preparation temperature) and the characteristics of the Si substrate (doping type, doping level).