Hydrogenated amorphous carbon thin films deposited by plasma-assisted chemical vapor deposition enhanced by electrostatic confinement: structure, properties, and modeling

Hydrogenated amorphous carbon (a-C: H) is a state-of-the-art material with established properties such as high mechanical resistance, low friction, and chemical inertness. In this work, a-C: H thin films were deposited by plasma-assisted chemical vapor deposition. The deposition process was enhanced by electrostatic confinement that leads to decrease the working pressure achieving relative high deposition rates. The a-C: H thin films were characterized by elastic recoil detection analysis, Rutherford backscattering spectroscopy, scanning electron microscopy, Raman spectroscopy, and nanoindentation measurements. The hydrogen content and hardness of a-C: H thin films vary from 30 to 45 at% and from 5 to 15 GPa, respectively. The hardness of a-C: H thin films shows a maximum as a function of the working pressure and is linearly increased with the shifting of the G-peak position and ID/IG ratio. The structure of a-C: H thin films suffers a clustering process at low working pressures. A physical model is proposed to estimate the mean ion energy of carbonaceous species arriving at the surface of a-C: H thin films as a function of processing parameters as pressure and voltage and by considering fundamentals scattering events between ion species and neutral molecules and atoms.