Protective diamond-like coatings for optical materials and electronic devices

The mechanical and protective properties of plasma enhanced chemical vapor deposition (PECVD) a-C:H films were studied in terms of their use as wear resistant and chemically inert coatings for optical and electronic products, The effect of the discharge power and gas mixture composition on the hardness and wear resistance of a-C:H films, as well as on the level of mechanical stresses in the film-substrate system, has been studied. By varying the synthesis parameters we have succeeded in obtaining films of hardness up to 16 GPa. Diamond-like films are shown to exceed monocrystalline silicon in wear resistance. Internal stresses in the film-substrate system attain 1 GPa. The introduction of nitrogen into the methane-hydrogen gas mixture causes the strength to increase and internal stresses to halve. Atomic force microscopy (AFM) was used to study variations in the surface morphology of a-C:H films synthesized under different conditions. The stability of a-C:H film to annealing in the air, light irradiation, chemically active etching solutions, and to environmental factors (enhanced humidity, salt fog, temperature, dynamic dust, etc.) was also studied. Diamond-like carbon (DLC) films have been applied to germanium products as external protective layers of infrared multilayer antireflection coatings. The use of DLC film as a barrier coating for the heating layer of inkjet print cartridges has enabled a tenfold increase in service life. (C) 2000 Elsevier Science S.A. All rights reserved.