High-field conduction and space charge distribution in acetophenone-coated polyethylene film

This paper describes the effect of polarity of applied field and electrode metal on electric conduction and space charge formation in one-sided acetophenone-coated low density polyethylene (LDPE) film. Up to an electric field of about 0.5 MV/cm with Au electrode, the acetophenone-coated positive electrode gives much larger conduction current than the negative one, suggesting that the existence of acetophenone at electrode interface enhances the hole injection rather than the electron injection. In the case of Al electrode this polarity dependence is opposite, suggesting the electron injection is more enhanced for Al electrode. Above about 0.5 MV/cm, however, these polarity effects changed. This change of polarity effect in high field region is explained by considering the space charge distribution and carrier injection from the acetophenone non-coated-side electrode. With the polarity where the current above 0.5 MV/cm became much larger, the dc electric strength showed significant decrease, showing that the dc breakdown is governed by the thermal process caused by Joule heating.