Synthesis of amorphous hydrogenated carbon (a-C: H) films on Germanium by the use of the linear anode layer source

A method for the synthesis of amorphous hydrogenated carbon (a-C:H) films with high adhesion is proposed, based on the implantation of carbon ions into a monocrystalline germanium substrate. The flow of ionized carbon was created by an anode layer ions source in crossed electric and magnetic fields. Propane gas was introduced into the area with an increased electron concentration. The gas flow rate varied from 4.5 to 10 sccm. Ionized fragments of propane, including carbon ions, were accelerated by the electric field and deposited on the substrate. At the same time, ionized carbon penetrated into the surface layer of germanium, creating an interlayer that provides film's adhesion. The substrate was argon sputtered for several minutes before the deposition. The synthesis of the coating includes two-stage process. At the first stage, the films were deposited by an ion beam with a mean energy of about 1.6 keV for 0.5 to 1 hour to obtain an adhesive interlayer. Then the mean energy of the beam was reduced to 0.3 keV and the deposition continued for 3.5 hours to maintain the hardness of the coatings. The deposition rate was changed from 0.3 to 1.3 Å /sec. Adhesion, the bond between the coating and the substrate is high. There is no detachment of the film while scratching by diamond Berkovich nanoindent with a load of up to 50 mN. The maximum film hardness is 20 GPa. Spectroscopic studies have shown the maximum transmission of germanium with a single side a-C:H coating is 67% at a wavelength of 5 μm, while bare substrate transmission is 51%. The results of the work can be applied in the creation of protective antireflective coatings of optical systems, the creation of medical implants and mechanical devices.