It, J1/T and JE characteristics for the understanding of the main mechanism of electric conduction and the determination of the glass transition temperature of parylene C thin films

摘要

Measurements under both transient and steady-state conditions on parylene C (H_2CC_6H_3ClCH_2)_n, also called PPX C, were made for different electric fields ranging from 8.33 to 33.33MVm~1. The transient current behaviour is hyperbolic in nature up to 125°C. Above, the current is transient free and becomes constant reflecting the presence of the steady state. The decay rate of the transient current increases with increasing temperature and field. The transient current is attributed mainly to the dipolar relaxation due to the polarization of the CCl dipole. The J1/T characteristic reflects the change in the conduction regime occurring at a critical temperature associated with the glass transition temperature of the materials. The JE measurements show that hopping conduction is the possible mechanism below and above T_g of parylene C. The activation energy is determined to be 0.13eV, independent of the electric fields below T_g and varies from 0.65 to 0.94eV above T_g, indicating the presence of more than one type of trapping centres in parylene C. The ionic jump distance a is estimated to be 5.606.68 below T_g and 8.3626.58 above T_g.