Conduction currents in fluorinated parylene PA-HT at high temperature

In this paper, transient current characteristics for fluorinated parylene (PA-HT) films are investigated in the temperature range between 200°C and 350°C as a function of the electric field, material thickness and electrode polarity using a non symmetrical metal/PA-HT/metal structure. In the transient domain, it is found that the decrease in the current during the bias time is mainly due to dipole orientation. For measured steady-state currents, the activation energy of the current density is calculated to be approximately equal to 1 eV and independent on the field in the range (100 kV/cm-1600 kV/cm) suggesting the ionic conduction mechanism. The ionic jump distance is extracted from the slope of the plot ln I-F and the values of 25 Å is found at 250°C and 300°C and 27 Å at 350°C. Those values are in good agreement with others obtained for other parylene films above the glass transition temperature. The film thickness does not affect significantly the dielectric properties in the studied range (1 to 5 μm), while the electrode polarity affects the current density for fields higher than 2 MV/cm.