In order to make clear the breakdown mechanism in plasma polymer films of ethylene and those of ethylene and trifluoromethane, high-field conduction, dielectric breakdown and photoconduction characteristics were studied. The attention was given to the determination of carrier species which causes avalanche. It was found that all these characteristics depend on the anode metal. When the anode is aluminum, the barrier height for tunneling injection obtained from the Fowler-Nordheim relation is higher than the gold anode. The aluminum anode also has a higher dielectric strength and a longer time lag to breakdown than the gold anode.
From these results, together with the effect of the shape of illuminated electrode on photocurrent, it is considered holes are injected through tunneling from the anode by high electric stress applied and that avalanche is caused by these holes.