Study of the structure, composition and wettability of the DLC:N films

Abstract

Encoders are widely used for measurements of very small displacements, position and movement speed in metrology instruments, motion systems, and high-precision machining tools, ranging from digital calipers to coordinate measuring machines. Optical scales are the most accurate encoders. Their effectiveness at a near-dew point is limited, thus hydrophilic coatings are being developed for proper instrument functioning at these conditions. Here, we study wetting and structural properties of nitrogen-doped DLC (DLC:N) films, produced with reactive magnetron sputtering (RMS) and inductively coupled plasma (ICP) beam-assisted magnetron sputtering as potential coatings for optical scale technologies. The slope parameter of the DLC:N films increases as the nitrogen content increases. The toughness of DLC:N coatings changes between methods used and is higher for samples when the RMS growth method is used. The DLC:N wetting varies from 33° to 58.8° for different nitrogen content in the DLC films. The increase in atomic nitrogen concentration increases the number of nitrogen-based functional groups and should lessen the hydrophobic influence of the CH group on the contact angle. Furthermore, CO and OH functional groups' promote even higher contact angle decline, hence it seems that introducing oxygen-based groups, encourages hydrophilicity of DLC films.