Surface Potential Decay of Corona Charged Polyethylene Films: Influence of Deep Surface Traps

Electret properties of low-density polyethylene (LDPE) films are investigated in the range of relatively low (up to 10
⁷
V/m) electrical fields. Thermally stimulated surface potential decay and thermally stimulated surface potential recovery reveal that LDPE films show no “cross-over” phenomenon and space charge accumulation in the polymer volume. The deepest traps with an energy of 1.1–1.2 eV are localized in the thin near-surface polymer layers. During poling (independent of the initial surface potential value), a part of the charge is captured in the deep traps that have limited concentration. Moreover, such deep traps can be filled also via the sequence of trapping and release events from the shallower traps located in the near-surface layer.