Concentration and mobility of charge carriers in thin polymers at high temperature determined by electrode polarization modeling

Abstract

Charge carrier concentration (n 0) and effective mobility (μ eff) are reported in two polymer films (10 μm) and in a very high temperature range (from 200 to 400 °C). This was possible thanks to an electrode polarization modeling of broadband dielectric spectroscopy data. It is shown that the glass transition temperature (T g) occurrence has a strong influence on the temperature dependence of n 0 and μ eff. We carry out that n 0 presents two distinct Arrhenius-like behaviors below and above T g, while μ eff exhibits a Vogel-Fulcher-Tamman behavior only above T g whatever the polymer under study. For polyimide films, n 0 varies from 1 × 10 14 to 4 × 10 16 cm -3 and μ eff from 1 × 10 -8 to 2 × 10 -6 cm 2 V -1 s -1 between 200 °C to 400 °C. Poly(amide-imide) films show n 0 values between 6 × 10 16 and 4 × 10 18 cm -3 from 270 °C to 400 °C, while μ eff varies between 1 × 10 -10 and 2 × 10 -7 cm 2 V -1 s -1. Considering the activation energies of these physical parameters in the temperature range of investigation, n 0 and μ eff values appear as coherent with those reported in the literature at lower temperature (80 °C). Surface charge carrier concentrations (n S) are reported and discussed for potential passivation (i.e., surface electrical insulation) applications. Polyimide films appear as good candidates due to n S values less than 10 11 cm -2 up to 300 °C. © 2012 American Institute of Physics.