Formation of the TaN/MgO(001) interface at the atomic scale

First-principles calculations of the TaN/MgO(001) interface were conducted using density functional theory. A thermodynamic stability analysis identified four energetically favorable interface models, with the most stable configuration featuring a TaO monolayer between the TaN and MgO layers. All interface models exhibit a metallic behavior, as indicated by the density of states at the Fermi level; in addition, the electron localization function reveals ionic bonding across the interface. Accompanying the simulations, TaN ultrathin films were grown epitaxially on FCC MgO(001) substrates using pulsed laser deposition. A cross-sectional transmission electron microscopy characterization confirms that the TaN films present an epitaxial relationship with the MgO substrate, which is TaN[001]||MgO[001]. Furthermore, a fast Fourier transform analysis shows that the TaN lattice contracts at the interface to match the MgO lattice, being consistent with the computational predictions. Our findings suggest that strained TaO layers play a critical role in stabilizing the TaN/MgO(001) interface.