Adatom-Driven Oxygen Intermixing during the Deposition of Oxide Thin Films by Molecular Beam Epitaxy

Thin film deposition from the vapor phase is a complex process involving adatom adsorption, movement, and incorporation into the growing film. Here, we present quantitative experimental data that reveals anion intermixing over long length scales during the deposition of epitaxial Fe2O3 and Cr2O3 films and heterostructures by oxygen-plasma-assisted molecular beam epitaxy. We track this diffusion by incorporating well-defined tracer layers containing O-18 and/or Fe-57 and measure their redistribution on the nanometer scale with atom probe tomography. Molecular dynamics simulations suggest potential intermixing events, which are then examined via nudged elastic band calculations. We reveal that adatoms on the film surface act to pull up subsurface O and Fe. Subsequent ring-like rotation mechanisms involving both adatom and subsurface anions then facilitate their mixing. In addition to film deposition, these intermixing mechanisms may be operant during other surface-mediated processes such as heterogeneous catalysis and corrosion.

Automated summary

Thin film deposition from the vapor phase involves complex adatom adsorption, movement, and incorporation into the growing film. This study provides experimental and simulation evidence for anion intermixing during the deposition process. The research reveals that adatoms on the film surface pull up subsurface oxygen and iron and facilitate their mixing through ring-like rotation mechanisms. These findings contribute to the understanding of thin film deposition and other surface-mediated processes.