In situ monitoring of atomic layer epitaxy via optical ellipsometry

TL;DR

This paper demonstrates real-time monitoring of atomic layer epitaxy using optical ellipsometry, providing detailed insights into film growth, structure, and defects with subatomic sensitivity.

Contribution

It introduces a novel application of time-resolved optical ellipsometry for in situ monitoring of atomic layer deposition, validated by ex situ characterization.

Findings

Successful real-time monitoring of atomic layer growth.

Correlation between ellipsometry data and film structure.

Validation of optical model with TEM, XRD, and XRR.

Abstract

We report on the use of time-resolved optical ellipsometry to monitor the deposition of single atomic layers with subatomic sensitivity. Ruddlesden-Popper thin films of SrO(SrTiO3)n=4 were grown by means of metalorganic aerosol deposition in the atomic layer epitaxy mode on SrTiO3(100), LSAT(100) and DyScO3(110) substrates. The measured time dependences of ellipsometric angles, ${\Delta}(t)$ and ${\Psi}(t)$, were described by using a simple optical model, considering the sequence of atomic layers SrO and TiO2 with corresponding bulk refractive indices. As a result, valuable online information on the growth process, the film structure and defects were obtained. Ex situ characterization techniques, i.e. transmission electron microscopy (TEM), X-ray diffraction (XRD) and X- ray reflectometry (XRR) verify the crystal structure and confirm the predictions of optical ellipsometry.