X-ray photoemission study of CoFeB/MgO thin film bi-layers

TL;DR

This study uses X-ray photoemission spectroscopy to analyze the formation and control of oxides and B content at the CoFeB/MgO interface in thin film bi-layers, revealing process-dependent oxidation and methods to manipulate interface composition.

Contribution

It provides new insights into interface oxidation processes and demonstrates how inserting an Mg layer can control B content in the MgO barrier.

Findings

Oxide formation at the interface depends on the deposition process.

Vacuum annealing reduces metal oxides but increases B incorporation.

Inserting Mg acts as an oxygen sink, controlling B content.

Abstract

We present results from an X-ray photoemission spectroscopy (XPS) study of CoFeB/MgO bi-layers where we observe process-dependent formation of B, Fe, and Co oxides at the CoFeB/MgO interface due to oxidation of CoFeB during MgO deposition. Vacuum annealing reduces the Co and Fe oxides but further incorporates B into the MgO forming a composite MgBxOy layer. Inserting an Mg layer between CoFeB and MgO introduces an oxygen sink, providing increased control over B content in the barrier.