Dielectric relaxation in hard, plasma-polymerized C:H films

The dielectric relaxation in hard, plasma-polymerized C:H films has been studied using the depolarization current method. These films were prepared by means of a dc unbalanced magnetron operated in a working gas mixture of Ar with n-hexane. The C:H films were sandwiched between two thin, aluminium-film electrodes. The measurements took place without breaking vacuum at temperatures ranging from 22 °C to 140 °C. The analysis of the respective depolarization currents was performed by means of the Kohlrausch-Williams-Watts depolarization function. Two dielectric relaxation processes were observed. The first is associated with high-dipole polar groups such as hydroxyl and carbonyl groups. The second relaxation process is observed only at the highest temperatures and cannot be explained in terms of permanent dipole reorientation. This finding shows that the C:H films are hard, highly crosslinked hydrocarbon plasma polymers.