Measurements of Thickness, Surface Roughness and Corrosion Performance of 1-10 nm Thick CN_x Films

Nitrogenated carbon (CN_x) films were synthesized by using pulsed dc magnetron sputtering. When grown with substrate tilt of 45° and rotation speed of 20–25 rpm, the root-mean-square surface roughness is ∼0.3 nm when sampled over 20×20 μm² areas, increasing to ∼0.4 nm when sampled over ∼0.05×3 cm² using x-ray reflectivity measurements. X-ray reflectivity measurements showed that the mass density of these CN_x films is ∼2.0 gm/cc, independent of film thickness from ∼1 to 10 nm, consistent with ion beam analysis. CN_x films deposited with substrate tilt of 45° and rotation speed of 20–25 rpm have about 1/3 fewer corrosion spots per unit area than those without. Reducing CN_x thickness from 3 to 1 nm results in marked increase in corrosion currents.