Sr flux stability against oxidation in oxide-MBE environment: flux, geometry, and pressure dependence

TL;DR

This study investigates how flux stability of strontium in oxide-MBE is affected by flux level, geometry, and pressure, revealing conditions that minimize oxidation and improve flux control.

Contribution

It provides a systematic analysis of factors influencing Sr flux stability, offering practical guidelines for reducing source oxidation in oxide-MBE processes.

Findings

Higher flux reduces oxidation.

Extended port geometry minimizes flux transients.

Oxidation occurs more on crucible walls than on source surface.

Abstract

Maintaining stable fluxes for multiple source elements is a challenging task when the source materials have significantly different oxygen affinities in a complex-oxide molecular-beam-epitaxy (MBE) environment. Considering that Sr is one of the most easily oxidized and widely used element in various complex oxides, we took Sr as a probe to investigate the flux stability problem in a number of different conditions. Source oxidation was less for higher flux, extended port geometry, and un-melted source shape. The extended port geometry also eliminated the flux transient after opening a source shutter as observed in the standard port. We also found that the source oxidation occurred more easily on the crucible wall than on the surface of the source material. Atomic oxygen, in spite of its stronger oxidation effectiveness, did not make any difference in source oxidation as compared to molecular oxygen in this geometry. Our results may provide a guide for solutions to the source oxidation problem in oxide-MBE system.