Effect of the modulation ratio on the interface structure of TiAlN/TiN and TiAlN/ZrN multilayers: First-principles and experimental investigations

The interface structure of the multilayered transition metal nitride coatings, which are widely used for various industrial applications, plays a crucial role in their properties. Here, first-principles calculations combined with key experiments are used to investigate the interface structures of TiAlN/TiN and TiAlN/ZrN multilayers with varied modulation ratios. Based on first-principles energetics calculations, it was found that TiAlN/TiN multilayers favour the coherent growth, independent of the modulation ratio of TiAlN to TiN, whereas the modulation ratio of TiAlN to ZrN has an important effect on the interface structure of TiAlN/ZrN multilayers. This prediction is in agreement with our experimental investigations. For TiAlN/TiN and TiAlN/ZrN multilayers with modulation periods of 4-6 nm and varied modulation ratios, the coherent interfaces between the TiAlN and TiN sublayers are observed in all TiAlN/TiN multilayers, while only the TiAlN/ZrN multilayer with a lower modulation ratio of TiAlN to ZrN exhibits the overall metastable epitaxial growth. The formation of metastable coherent interfaces in TiAlN/ZrN multilayers can be attributed to the nonequilibrium deposition process with the presence of defects, such as interface dislocations.

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