First-principles calculations on the electronic structure and bonding nature of TaN(111)/TiN(111) interface

The work of adhesion, electronic structure, and bonding nature of TaN(111)/TiN(111) interfaces have been investigated by means of the first-principles calculations. Taking into account three atom stacking sites (OT-, SL-, and TL-sites) and two terminations (Ta/N and N/Ti), we calculate six possible candidate configurations. It is found that the stacking sequence is the dominating factor on the work of adhesion for TaN(111)/TiN(111) interfaces. The most stable interface configuration, viz., that having the largest work of adhesion and the smallest interfacial separation (5.15 and 5.95 J/m2, 1.37 and 1.11 Å, for Ta/N and N/Ti termination systems, respectively), is TL site, in which the interfacial atom stacking sequence retains the order of the nitride bulks. The interfacial bonding nature of the stable Ta/N and N/Ti interfacial structures has been systematically investigated based on the calculations of the charge density, the charge density difference, the partial density of states, and the Mulliken population. An enhanced covalent bonding interaction has deduced between the interfacial Ta and N atoms in Ta/N interface, while an enhanced ionic bonding is found between the interfacial N and Ti atoms in N/Ti interface. The bond length between the interfacial N and Ti atoms in N/Ti configuration is evidently shorter than that of the TiN inner. The calculation results presented here would provide useful knowledge on the bonding nature of TaN(111)/TiN(111) interface, and may be helpful for further understanding and improving the TaN/TiN multilayered coatings.