Crucible aperture: an effective way to reduce source oxidation in oxide molecular beam epitaxy process

TL;DR

This paper demonstrates that using a crucible aperture insert in oxide-MBE significantly reduces source oxidation, leading to over four times improved flux stability for Sr sources, enhancing the control of multi-elemental oxide growth.

Contribution

The study introduces a crucible aperture insert method that effectively minimizes source oxidation in oxide-MBE, improving flux stability for elements with high oxygen affinity.

Findings

Over four times improvement in Sr flux stability with aperture

Aperture depth is critical for performance

Significant reduction of source oxidation in oxide-MBE

Abstract

Growing multi-elemental complex-oxide structures using an MBE (Molecular Beam Epitaxy) technique requires precise control of each source flux. However, when the component elements have significantly different oxygen affinities, maintaining stable fluxes for easily oxidizing elements is challenging because of a source oxidation problem. Here, using Sr as a test source, we show that a crucible aperture insert scheme significantly reduces the source oxidation in an oxide-MBE environment. The crucible aperture insert was shaped like a disk with a hole at the center and was mounted inside the crucible; it blocks most of the oxygen species coming to the source, thus reducing the source oxidation. However, the depth of the aperture disk was critical for its performance; an ill-positioned aperture could make the flux stability even worse. With an optimally positioned aperture insert, the crucible exhibited more than four times improvement in Sr flux stability, compared to a conventional, non-apertured crucible.