Simple self-gettering differential-pump for minimizing source oxidation in oxide-MBE environment

TL;DR

The paper introduces a self-gettering differential pump for oxide-MBE that effectively prevents source oxidation by using the source as a self-pumping medium, ensuring flux stability in oxidizing environments.

Contribution

A novel self-gettering differential pump design that eliminates source oxidation in oxide-MBE by using the source itself as the pumping medium.

Findings

Maintains oxygen partial pressure below oxidation threshold.

Achieves flux stability comparable to ultra-high vacuum.

Self-feedback mechanism enhances pumping for oxidizing elements.

Abstract

Source oxidation of easily oxidizing elements such as Ca, Sr, Ba, and Ti in an oxidizing ambient leads to their flux instability and is one of the biggest problems in the multi-elemental oxide Molecular Beam Epitaxy technique. Here we report a new scheme that can completely eliminate the source oxidation problem: a self-gettering differential pump using the source itself as the pumping medium. The pump simply comprises a long collimator mounted in front of the source in extended port geometry. With this arrangement, the oxygen partial pressure near the source was easily maintained well below the source oxidation regime, resulting in a stabilized flux, comparable to that of an ultra-high-vacuum environment. Moreover, this pump has a self-feedback mechanism that allows a stronger pumping effectiveness for more easily oxidizing elements, which is a desired property for eliminating the source oxidation problem.