Thickness dependence of surface diffusion in epitaxial LaAlO3 on SrTiO3(001)

TL;DR

This study investigates how the thickness of LaAlO3 films affects surface diffusion during epitaxial growth on SrTiO3(001), revealing layer-dependent diffusion rates and activation energies through in situ x-ray scattering techniques.

Contribution

It introduces a novel in situ measurement approach to quantify surface diffusion parameters as a function of film thickness in LaAlO3/SrTiO3 heterostructures.

Findings

Downhill diffusion rate of the first monolayer differs from subsequent layers.

Activation energies vary with LaAlO3 thickness.

Surface diffusion characteristics are comparable to homoepitaxial SrTiO3 deposition.

Abstract

The LaAlO3/SrTiO3 (001) thin film materials system was studied using in situ, simultaneous x-ray diffuse scattering and specular reflectivity during pulsed laser deposition. Using this method, we are able to measure the time dependence of the characteristic surface length scale and the characteristic time for both in-plane and downhill diffusion. These data allow for the determination of the activation energy for various diffusion processes as a function of LaAlO3 thickness. Additionally, we show that the downhill diffusion rate of the first monolayer is distinctly different than subsequent layers. These results are directly compared to previous experimental observations seen during the deposition of homoepitaxial SrTiO3 (001).