First-principles study of polar Al/TiN(1 1 1) interfaces

This research purposes to investigate the optimal atomic structure, work of adhesion, electronic property and stability of polar Al/TiN(1 1 1) interfaces by density functional theory. The results were then compared with non-polar Al/TiN(0 0 1) interfaces. The outcome shows that the polar interface structure which most resembles the ceramic stacking sequence across the interface has the strongest adhesion. Due to high surface energies, adhesion energies of polar Al/TiN(1 1 1) interfaces are larger than those of Al/TiN(0 0 1) interfaces. A thorough study of the electronic structure reveals that the N-terminated interface is the polar covalent bond, and the Ti-terminated interface mainly shows the metallic covalent interaction. The formation mechanism of interfacial AlN layer has also been well considered. Finally, thermodynamic examination shows that stabilities of both polar TiN(1 1 1) surfaces and Al/TiN(1 1 1) interfaces depend on the nitrogen chemical potential. This fact explains well the available experimental results.