Structural and mechanical properties of TaZrN films: Experimental and ab initio studies

This paper reports on the growth and characterization of the structural and mechanical properties of tantalum zirconium nitride films and the subsequent simulation of these properties using an ab initio calculation based on density functional theory (DFT) within the generalized gradient approximation. The films were deposited by reactive unbalanced magnetron sputtering and their physical and chemical properties were studied by means of x-ray diffraction (XRD), Rutherford backscattering (RBS), and nanoindentation. XRD revealed that these films formed a solid solution and that the lattice constant decreased linearly with Ta content. RBS provided the elemental composition of the films. Nanoindentation was used to evaluate the hardness and the elastic modulus. The hardness was found to have high values for a Ta/(Ta+Zr) of 30% and 100%. The elastic modulus was found to increase monotonically with Ta content. The intrinsic elastic constants were calculated using DFT and the results were compared to the experimental values. A correlation between the computational and the experimental Young's modulus was established. However, the trends observed for the measured hardness and the calculated shear modulus were not in agreement. This disagreement was due to the prominent extrinsic component of the hardness for these materials. (c) 2006 American Institute of Physics.