Template-induced coherent growth and mechanical properties of ZrO2/TiN nano-multilayers

 ZrO2/TiN nano-multilayers with various TiN layer thicknesses were synthesized. Studies reveal that the usual rocksalt structure of TiN at very low thickness (<∼1.8 nm) is transformed into a pseudocrystal, with the same structure as tetragonal ZrO2, and grows coherently with ZrO2 layers. As the thickness of the TiN layer increases further, TiN gradually grows into rocksalt structure, blocking the coherent growth of multilayers. The superhardness effect was not obtained in ZrO2/TiN nano-multilayers, since the coherent strains in multilayers could reduce the modulus difference between their constituents.