Diamond-like carbon （DLC） films have been deposited using three different techniques： （a） electron cyclotron resonance——plasma source ion implantation, （b） low-pressure dielectric barrier discharge, （c） filtered——pulsed cathodic arc discharge, The surface and mechanical properties of these films are compared using atomic force microscopebased tests. The experimental results show that hydrogenated DLC films are covered with soft surface layers enriched with hydrogen and sp^3 hybridized carbon while the soft surface layers of tetrahedral amorphous carbon （ta-C） films have graphite-like structure, The formation of soft surface layers can be associated with the surface diffusion and growth induced by the low-energy deposition process. For typical CVD methods, the atomic hydrogen in the plasmas can contribute to the formation of hydrogen and sp^3 hybridized carbon enriched surface layers, The high-energy ion implantation causes the rearrangement of atoms beneath the surface layer and leads to an increase in film density. The ta-C films can be deposited using the medium energy carbon ions in the highly-ionized plasma.
Atomic force microscopy is used to estimate and compare the surface morphology of hydrogenated and hydrogen-free diamond-like carbon （DLC） films. The films were prepared by using DC magnetron sputtering of a graphite target, pulsed cathodic carbon arcs, electron cyclotron resonance （ECR）, plasma source ion implantation and dielectric barrier discharge （DBD）. The difference in the surface structure is presented for each method of deposition. The influences of various discharge parameters on the film surface properties are discussed based upon the experimental results. The coalescence process via the diffusion of adsorbed carbon species is responsible for the formation of hydrogen-free DLC films with rough surfaces. The films with surface roughness at an atomic level can be deposited by energetic ion impacts in a highly ionized carbon plasma. The hydrocarbon species dangling bonds created by atomic hydrogen lead to the uniform growth of at the a-C：H film surfaces of the ECR or DBD plasmas
Plasma polymerized fluorocarbon （FC） films have been deposited on silicon substrates from dielectric barrier discharge （DBD） plasma of C4Fs at room temperature under a pressure of 25～125 Pa. The effects of the discharge pressure and frequency of power supply on the films have been systematically investigated. FC films with a less cross linked structure may be formed at a relatively high pressure. Increase in the frequency of power supply leads to a significant increase in the deposition rate. Static contact angle measurements show that deposited FC films have a stable, hydrophobic surface property. All deposited films show smooth surfaces with an atomic surface roughness. The relationship between plasma parameters and the properties of the deposited FC films are discussed.
The kinetic energy of ions in dielectric barrier discharge plasmas are analysed theoretically using the model of binary collisions between ions and gas molecules. Langevin equation for ions in other gases, Blanc law for ions in mixed gases, and the two-temperature model for ions at higher reduced field are used to determine the ion mobility. The kinetic energies of ions in CH4 ＋ Ar（He） dielectric barrier discharge plasma at a fixed total gas pressure and various Ar （He） concentrations are calculated. It is found that with increasing Ar （He） concentration in CH4 ＋ Ar （He） from 20% to 83%, the CH4＋ kinetic energy increases from 69.6 （43.9） to 92.1 （128.5）eV, while the Ar＋ （He＋） kinetic energy decreases from 97 （145.2） to 78.8 （75.5）eV. The increase of CH4＋ kinetic energy is responsible for the increase of hardness of diamond-like carbon films deposited by CH4 ＋ Ar （He） dielectric barrier discharge without bias voltage over substrates.
