Deposition of diamond-like carbon films by low energy ion beam and d.c. magnetron sputtering

Abstract

Amorphous diamond-like carbon films were prepared using low energy (1.0–1.25 keV) ion beam plasma of hydrocarbons (methane and n-butane) and by d.c. magnetron sputtering of a graphite target in argon plasma. Optical measurements of the refractive indices n and k in the photon energy 1.0–4.0 eV are reported. The optical properties of sputtered films shows a dependence on sputtering power. The optical gap E opt for sputtered films was found to be 0.78 eV and the gap increased to 1.27 eV for ion-beam-deposited films. Knoop hardness was determined for different loads, and it varied from 1000–2500 kgf mm -2. Internal stress measurements were also performed. Films prepared by magnetron sputtering were found to have high compressive stress which depended on the partial pressure of the sputtering gas. A typical value of the internal stress in ion beam films prepared from butane plasma was 2.0 × 10 9 N m -2. The effective number of valency electrons per carbon atom n eff, was calculated and the ratio of fourfold sp 3 to threefold sp 2 coordination of carbon atoms was found to be 8.08. The application of these films as a corrosion resistant coating and a single layer antireflection coating on germanium for 10.6 μm wavelength was demonstrated.