Epitaxial stabilization of cubic-SiNx in TiN/SiNx multilayers

The formation of cubic-phase SiNx is demonstrated in TiN/SiNx multilayers deposited by reactive dual magnetron sputtering. Transmission electron microscopy examination shows a transition from epitaxially stabilized growth of crystalline SiNx to amorphous growth as the layer thickness increases from 0.3 to 0.8 nm. The observations are supported by ab initio calculations on different polytypes, which show that the NaCl structure has the best lattice match to TiN. Calculations also reveal a large difference in elastic shear modulus between NaCl-SiNx and TiN. The results for phase structure and shear modulus offer an explanation for the superhardening effect determined by nanoindentation experiments. (c) 2006 American Institute of Physics.