Microstructure and mechanical properties of TiAlN/Si 3N 4 nano-multilayers synthesized by reactive magnetron sputtering

Abstract

TiAlN/Si 3N 4 nano-multilayers with various Si 3N 4 layer thicknesses were synthesized by reactive magnetron sputtering. The composition, microstructure, and mechanical properties of the films were studied by energy dispersive X-ray spectroscopy, X-ray diffraction, scanning electron microscopy, and nanoindentation. It reveals that under the template effect of TiAlN layers in multilayers, as-deposited amorphous Si 3N 4 is crystallized and grows coherently with TiAlN layers when Si 3N 4 layer thickness is below 0.9 nm. Correspondingly, the hardness and elastic modulus of the multilayers increase abnormally and reach the maximum values of 52 and 588 GPa, respectively. With further increase in the layer thickness, Si 3N 4 transforms into amorphous and blocks the coherent growth of multilayers, resulting in a decrease of hardness and modulus. The remarkable hardness enhancement of multilayers is correlated to the crystallization of Si 3N 4, and the coherent strain in multilayers that could change the modulus of two constituents.