Magnetron sputtered NbN thin films and mechanical properties

In this study, NbN thin films were deposited by reactive magnetron sputtering at different N-2 partial pressures and at room temperature. X-Ray diffraction analysis, transmission electron microscopy and atomic force microscopy were employed to characterize their phases, microstructure and surface morphology. Their microhardness and elastic modulus were evaluated using a microhardness tester and the effects of N-2 partial pressure on the phase formation, microstructure and mechanical properties of NbN thin films were investigated. The results show that there are clear effects of N-2 partial pressure on the deposition rate, phases, hardness and elastic modulus of magnetron sputtered NbN films. At a low N-2 partial pressure, the deposition rate is higher, while hcp beta-Nb2N and fcc delta-NbN coexist in NbN films. With the increase of N-2 pressure, the deposition rate decreases and the films are single-phase fcc deltaNbN; accordingly, the hardness and modulus reach peak values of 36.6 GPa and 457 GPa, respectively. A further increase of the N-2 partial pressure will cause hcp epsilon-NbN to appear in NbN films and then the hardness and modulus of films decrease. (C) 2003 Elsevier B.V. All rights reserved.