Digging into the Atomistic Details of the TaN/MgO Interface: An Ab Initio Study Supported by Transmission Electron Microscopy

First-principles calculations of the TaN/MgO (001) interface were performed within the DFT framework. A thermodynamic stability analysis identified four stable interfaces. The most stable configuration for the interface consists of a TaO monolayer formed between the TaN and MgO layers. The density of states at E_F indicates that all interface models exhibit metallic behavior. The electron localization function reveals that all of these models exhibit ionic-type bonds at the interface. In addition to the computational simulations, epitaxial growth of the TaN thin films on FCC MgO (001) substrates was carried out by using pulsed laser deposition. Transmission electron microscopy images of the TaN/MgO (001) interface cross-section reveal that TaN film grows on the MgO substrate following the epitaxial relationship TaN [001] || MgO [001]. An FFT analysis of the TaN films demonstrates that the TaN lattice contracts at the interface with MgO conforming to the substrate lattice, corroborating the computational predictions. Our results provide evidence that strained TaO layers mediate the TaN/MgO (001) interface formation.