TEMPERATURE-DEPENDENCE ANALYSIS OF THE ELECTRON-PARAMAGNETIC-RESONANCE SIGNAL AND ELECTRICAL-CONDUCTIVITY IN AC AND A-C-H

In this paper, a study of the electron paramagnetic resonance (EPR) signal and of the electrical conductivity for sputtered amorphous carbon (a-C) and graphite-like amorphous hydrogenated carbon (a-C:H) films is reported. In particular, the comparison of the temperature dependence of conductivity and of the EPR resonance signal line width shows that different mechanisms are responsible for conduction in the two materials. Conduction is by overlapping states in a-C down to 60 K and by hopping in a-C:H up to 400 K. Further differences are observed in the spin-lattice relaxation times in the whole temperature range from 10 to 500 K where the values in a-C:H were found longer by an order of magnitude as compared with those in a-C.