Influence of plasmas on the surface of electret films

Summary form only given. In the corona charging of electret films, the high voltage results in plasma in the air. The plasmas near the surface of the charged film have the double influences on the sample. On the one hand, the charged ions deposit on the surface of the polymer electret film and injected into it, which make the sample to become good electrets. On the other hand, the plasmas may injure the surface of the sample, which is harmful to the deposition and permanent storage of charges near the surface of the film. The theoretical analysis and experiments show the control of exerted voltage during the corona charging is very important to the result. The critical voltage that is best for the storage of charges, is found to depend on the shape of the electrode of discharging and the distance to the sample. It is interesting that the negative voltage of corona charging has less negative influence on the surface of Teflon samples than the positive one. We think that the kind of negative ions in the plasmas result in the phenomena