The structure and stability of beta-Ta thin films

TL;DR

This study investigates the structure and stability of beta-Ta thin films deposited on various substrates, revealing their preferred orientation, crystal structure, defect presence, and stability through experimental and simulation methods.

Contribution

It provides new insights into the preferred orientation, crystal structure, and stability mechanisms of beta-Ta thin films using combined experimental and molecular dynamics simulation approaches.

Findings

Beta-Ta films exhibit a strong (001) orientation.

The films favor the P-421m space group over P42/mnm.

Molecular dynamics simulations confirm the stability of beta-Ta.

Abstract

Ta films with tetragonal crystalline structure (beta-phase), deposited by magnetron sputtering on different substrates (steel, silicon and silicon dioxide), have been studied. In all cases, very highly preferred (001) orientation was observed in x-ray diffraction (XRD) measurements. All diffraction data revealed two weak reflections corresponding to d-spacing of 0.5272 and 0.1777 nm. The presence of the two peaks, attributed to (001) and (003) reflections, indicates that beta-Ta films exhibit a high preference for the space group of P-421m over P42/mnm, previously proposed for beta-Ta. Differences in relative intensities of (00l) reflections, calculated for single crystal beta-Ta sigma-type Frank-Kasper structure and those measured in the films, are attributed to defects in the films. Molecular dynamics simulations performed on tantalum clusters with six different initial configurations using the embedded-atom-method (EAM) potential revealed the stability of beta-Ta, which might explain its growth on many substrates under various deposition conditions.