Dynamic Interface Rearrangement in LaFeO$_3$ / $n$-SrTiO$_3$ Heterojunctions

TL;DR

This study demonstrates that precise control over atomic rearrangements at LaFeO3/n-SrTiO3 heterojunctions can be achieved through shuttered molecular beam epitaxy, revealing new insights into interface stabilization and growth kinetics.

Contribution

It shows how deposition timescales influence interface structure and stability, advancing understanding of growth pathways in complex oxide heterostructures.

Findings

Predominant LaO/TiO2 interface observed regardless of substrate termination.

Oxygen trapping and vacancy formation stabilize different interface configurations.

Control of deposition timescales can modify growth pathways and interface properties.

Abstract

Thin film synthesis methods developed over the past decades have unlocked emergent interface properties ranging from conductivity to ferroelectricity. However, our attempts to exercise precise control over interfaces are constrained by a limited understanding of growth pathways and kinetics. Here we demonstrate that shuttered molecular beam epitaxy induces rearrangements of atomic planes at a polar / non-polar junction of LaFeO$_3$ (LFO) / $n$-SrTiO$_3$ (STO) depending on the substrate termination. Surface characterization confirms that substrates with two different (TiO$_2$ and SrO) terminations were prepared prior to LFO deposition; however, local electron energy loss spectroscopy measurements of the final heterojunctions show a predominantly LaO / TiO$_2$ interfacial junction in both cases. Ab initio simulations suggest that the interfaces can be stabilized by trapping extra oxygen (in LaO / TiO$_2$) and forming oxygen vacancies (in FeO$_2$ / SrO), which points to different growth kinetics in each case and may explain the apparent disappearance of the FeO$_2$ / SrO interface. We conclude that judicious control of deposition timescales can be used to modify growth pathways, opening new avenues to control the structure and properties of interfacial systems.