Abstract: A microstructure investigation of TiN/Si₃N₄ nanocomposite films with high hardness was performed by means of high-resolution transmission electron microscope, and a result far from the nc-TiN/a-Si3N4 model was presented. Instead of the isotropic one, TiN was pronounced nanocrystalline columnar grains with dimensions of <10nm in width and >100nm in length. Immiscible Si₃N₄ interfacial phases between TiN nanocolumns with a thickness of about 0.5--0.7nm existed in nanocrystalline structure and formed coherent interfaces with adjacent TiN nanocrystals. A succedent simulation employing two-dimensional TiN/Si₃N₄ nanomultilayers also implied that due to the template effect of crystalline TiN layers, sputter-deposited amorphous Si₃N₄ was forced to crystallize and grow epitaxially with TiN layers when its thickness was less than 0.7nm, accompanied by a significant enhancement in film’s hardness. Due to the short-range nature of the template effect of TiN layers, the
crystalline Si3N4 gradually transformed into amorphous when its thickness exceeded 1.0nm and the coherent interfaces were destroyed as a consequence, with a simultaneous film’s hardness decline. By comparing the microstructure and corresponding hardness response of TiN/Si₃N₄ nanocomposite films with that of the nanomultilayered ones, a new explanation on hardening mechanism of TiN/Si₃N₄ nanocomposites was proposed.

Key words: TiN/Si3N4 nanocomposites, TiN/Si3N4 nanomultilayers, interfacial phase, crystallization, superhardness effect