Increase of nanometer-scale wear of polished chemical-vapor-deposited diamond films due to nitrogen ion implantation

In an effort to produce wear-resistant and lubricating surfaces, polished chemical-vapor-deposited (CVD) diamond films are implanted with nitrogen ions (N⁺). The influence of N⁺-implantation on tribological properties is then investigated. N⁺-implantation decreases the friction coefficient and increases the critical stress evaluated from surface scar formation by macroscopic reciprocal sliding. In contrast, the microwear of diamond films increases with N⁺-implantation, as evaluated by an atomic force microscope. Wear grooves are formed on the N⁺-implanted surface by diamond tip sliding. The results indicate a relationship between the depth of maximum shear strength and the depth of the damaged layer formed by N⁺-implantation.