Titanium boron nitride films grown by ion beam assisted deposition: Chemical and optical characterization

Titanium boron nitride films with a functionally graded underlayer of Ti/TiN were grown at low temperatures (<200 °C) on a silicon substrate using ion beam assisted deposition. These coatings had a total thickness of 1.5 ± 0.2 μm. They were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. The primary phases in the film were identified using XRD and were found to be in agreement with the equilibrium phase diagram. The surface morphology and nanocrystalline nature of the coating were deduced using AFM. The chemical and phase composition was determined from XPS measurements. The refractive indices were deduced from the investigation of the ellipsometric data and were subsequently correlated to the elemental and phase composition. The hardness and elastic modulus were measured and were found to depend on phase composition. The films were implanted with carbon ions. XPS measurements revealed that new phases formed at the surface as a result of carbon implantation, namely, titanium carbide and elemental carbon. Carbon implantation significantly reduced the friction coefficient from 0.5-0.7 to 0.15-0.25. The hardness of the films decreased by 2-5%.