Structural variations in CrN/NbN superlattices

The structure and properties of multilayer films of chromium nitride/niobium nitride has been investigated by X-ray diffraction (XRD), nanoindentation and atomic force microscopy. The films were deposited in a closed field unbalanced magnetron system using opposing chromium and niobium targets in an atmosphere containing nitrogen. It was found that the definition of the superlattice as defined by the intensity of its XRD diffraction peak is a linear function of the superlattice period and that below 10 إ there is no discernable layer structure due largely to ion mixing. The films show only a single set of diffraction peaks characteristic of face-centred cubic material with a lattice constant intermediate between that of CrN and NbN. The nanoindentation hardness shows no significant variation with superlattice period; the main effect on hardness is due to ion energy. The film structure changes from a rough columnar structure at low ion energies to a denser, smoother structure at higher bias and ion/atom ratio.