Structure and mechanical properties of dual-ion-beam deposited CN_xTi_y/TiN multilayers

CNxTiy/TiN multilayers have been synthesized using dual-ion-beam deposition. X-ray photoelectron spectra of C 1s, Ti 2p, N 1s, and Si 2p electrons were investigated against the depth from the film surface. The results confirm the layered structure of the films. The Ti atoms contained in a CNxTiylayer sandwiched between two TiN layers are expected to come from interlayer diffusion of Ti atoms enhanced by ion beam irradiation during deposition. As a consequence, a CNxTiylayer contains a C-N phase, a Ti-N phase, and a T-C phase. The C-N phase contains 27 at. % nitrogen, less than the level required to form the hypothetical β-C3N4phase, indicating that the multilayer structure containing TiN layers does not favor for increasing N content in the C-N phase of the CNxTiylayers. The Ti-N and Ti-C phases are about stoichiometric. The TiN layers comprise mainly a Ti-N phase, and a small fraction of the Ti-C phase, which are both stoichiometric. However, the bonding between C and N is weak. The hardness H and elastic modulus E of the films were investigated by nanoindentation experiments. The single-layer CN0.3is the softest (H=11.4 GPa), and the single-layer TiN is the hardest (H=22 GPa) among the samples in the series. H and E increase with increasing TiN volume fraction, as well as the number of interfaces. They also increase with increasing substrate temperature, possibly due to stronger interlayer diffusion of Ti atoms at higher temperature.