The effects of composition and pulsed biasing on chromium nitride films

Although chromium nitride (CrN) coatings are an industry standard for hard wear-resistant thin films, methods of improving/modifying film properties are still being sought therefore this study has investigated the effects of N2 flow and bias pulsing. Chromium nitride can exist in two stable forms, Cr2N and CrN, which have differing physical and tribological properties. The predominant structure depends on the nitrogen gas flow rate during deposition. Another process parameter known to influence film properties is the use of mid-frequency pulsed biasing (100–350 kHz) at the substrate, which can significantly increase the ion current drawn at the substrate during ion etching and deposition. This study has, therefore, investigated the effects of both nitrogen gas flow rate and the use of mid-frequency pulsed biasing (100–350 kHz) on the structure and properties of reactively sputtered chromium nitride films. We investigated the variation of target voltage with N2 flow, and the films have been characterised using SEM, XRD, scratch adhesion testing, profilometry, and nanoindentation.