Effect of the plasma confinement on properties of a-C:H:SiOx films grown by plasma enhanced chemical vapor deposition

Abstract

The properties of SiOx doped amorphous hydrogenated carbon (a-C:H:SiOx) films greatly depend on the deposition parameters, in particular, on the ion bombardment intensity during the film growth. In this work, a magnetic field created by an external magnetic coil was used for plasma confinement and control of the ion bombardment during the process of plasma enhanced chemical vapor deposition of a-C:H:SiOx films. The structure, surface morphology, and mechanical properties of the obtained films were studied using Raman spectroscopy, atomic force microscopy, and nanoindentation, respectively. This work shows that the increase in the magnetic field allows better confinement of the plasma and increased the density of the ion current on the substrate. It is shown that there is an optimal value of the magnetic field at which films with the best mechanical characteristics are formed. Higher magnetic field values lead to excessive heating of the substrate by the bombarded ions and graphitization of the film carbon matrix. Under optimum conditions, deposition of an a-C:H:SiOx film on an AISI 321 stainless steel substrate allowed increasing the hardness and plasticity index of its surface twice and its plastic deformation resistance by nine times. At the same time, the wear rate and the friction coefficient decreased by 25 and 5.5 times, respectively.