Interface effect on tribological properties of titanium–titanium nitride nanolaminated structures

Abstract Nanolaminated titanium–titanium nitride [Ti–TiN] n structures have been deposited on silicon 〈100〉 substrates by RF reactive sputtering in order to study their mechanical properties. Structures with graded Ti/TiN (interface thickness of approx. 2 nm) and with ultra-thin Ti/TiN interfaces (approx. 0.5 nm) have been investigated with multilayer period thicknesses ranging between 20 and 2.5 nm. The deposition followed by in situ kinetic ellipsometry point out the two types of interfaces. Real period thicknesses, measured by X-ray reflectometry, are close to the expected ones. Thin film X-ray diffraction analysis shows the polycrystalline nature of the nanostuctures. In the superlattice, Ti and TiN individual layers are textured [002] and [111], respectively. Tribological tests, carried out using a CSEM pin-on-disc apparatus, point out that the wear resistance of the samples increase when the period thickness is lowered (same total thickness and growth parameters). For small period thickness, the interface quality has a crucial influence on the wear resistance of the samples. Best tribological properties are observed for samples with ultra-thin interfaces and a period thickness of 2.5 nm.