Investigations on electrical properties of a-C:H thin films deposited in a Microwave Multipolar Plasma reactor excited at Distributed Electron Cyclotron Resonance

Abstract Amorphous hydrogenated carbon (a-C:H) thin films have been deposited from pure methane discharges in Microwave Multipolar Plasma excited at Distributed Electron Cyclotron Resonance (MMP-DECR). Investigations on the effect of process parameters on the film physico-chemical and electrical properties have been carried out. The plasma discharge power has a significant effect on the film density and on the concentrations of sp 3 - and sp 2 -hybridized carbon atoms. These latter (sp 3 and sp 2 fractions) are also dependant on the deposition time. A low sp 2 fraction was obtained in films deposited at high plasma discharge power and/or long deposition time. Moreover, increasing the plasma discharge power leads to less dense films. The film permittivity at 1 kHz is ranging from 3.8 to 2.3 depending on the two process parameters. This evolution of the dielectric constant is correlated to the film density and structure. The current voltage characteristics I ( V ) of Metal-Insulating-Metal structures using the different films suggest that the carrier transport in a-C:H thin films deposited by MMP-DECR is limited by a space charge conduction mechanism.