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

## TL;DR

This study combines computational modeling and microscopy to explore the atomic structure of the TaN/MgO interface and how it forms.

## Contribution

The study identifies a TaO monolayer as a key mediator in the formation of the TaN/MgO interface and confirms this with both simulations and experimental evidence.

## Key findings

- A TaO monolayer forms between TaN and MgO layers in the most stable interface configuration.
- All interface models show metallic behavior and ionic-type bonding at the interface.
- TaN films grow epitaxially on MgO substrates, with lattice contraction confirmed by microscopy and simulations.

## Abstract

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 EF 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.