Electrical properties of nitrogen-containing plasma polymer films

The electrical conductivity of plasma copolymerised films from allylamine and ethylene increases with an increase in the flow-rate of allylamine during the polymerisation, while the optical gap evaluated from optical absorption decreases. Deconvolution of infrared spectra showed that the ratio of sp² to sp³ carbons is not related to the nitrogen content of the film. This fact shows that the conductivity increase is not due to the development of conjugated carbon double bonds. It is deduced that the increase in conductivity is mainly caused by two different effects of the introduced nitrogen, i.e. the reduction in optical gap and the increase in unpaired electrons, both arising from the interaction between nitrogen atoms and conjugated carbon double bonds.