Nonstoichiometric amorphous silicon carbide films as promising antireflection and protective coatings for germanium in IR spectral range

Abstract

A technology for preparation of amorphous nonstoichiometric hydrogenated silicon carbide (a-SixC1-x:H) films using the PE-CVD method has been developed. Such films with refractive index n = 1.8–2.1 are suitable to obtain antireflection effect on germanium in the IR spectral region. Single- and two-sided antireflection coatings of Ge enabled to increase its optical transmission up to 65% and 96% in the maximum transmission, respectively. The obtained films have good mechanical properties (H > 12 GPa, E = 100 GPa). Presence of Si-C bonds in the a-SixC1-x:H films restricts their range of application to the spectral interval 2.5–10 μm. The prepared films are uniform in composition and have high adhesion to the substrate. Variation of deposition conditions makes it possible to obtain a-SixC1-x:H films having high hardness and Young's modulus. High deposition rate, optimal optical properties of the a-SixC1-x:H films and good combination of mechanical properties for the Ge/a-SixC1-x:H film structures make them to be promising for practical application as antireflection and protective coatings for germanium.