Identification of TSC peaks and surface-voltage stability in Teflon FEP

Abstract

In this paper we examine the stability of corona‐ and electron‐beam‐charged 25‐μm FEP‐A in open circuit by using thermally stimulated (TSC) measurements. We show that electrets charged with electron beams of 10 keV or higher are more stable than corona‐charged foils. The inferior stability of corona‐charged samples is due to the filling of surface traps as opposed to volume traps in electron‐beam‐charged samples. A peak at 155 °C was attributed to surface traps located at a depth of 0–0.5 μm, while a peak at 170 °C is due to charge stored 0.5–1.8 μm beneath the nonmetallized surface. The volume traps yield a peak at 200 °C. The total volume trap density was estimated to 1.4×10¹⁴ traps/cm³.