Tunneling spectroscopy studies of aluminum oxide tunnel barrier layers

TL;DR

This study uses tunneling spectroscopy techniques to analyze how surface electronic states of aluminum oxide tunnel barriers change with oxygen chemisorption and thermal treatments, revealing shifts in conduction band onsets.

Contribution

It provides detailed insights into the electronic state modifications of AlOx tunnel barriers due to oxygen chemisorption and thermal annealing, using advanced microscopy methods.

Findings

Chemisorbed oxygen shifts conduction band onset to ~1 V.

Thermal annealing raises conduction band onset above 2.3 V.

Surface electronic states are sensitive to oxygen and heat treatments.

Abstract

We report scanning tunneling microscopy and ballistic electron emission microscopy studies of the electronic states of the uncovered and chemisorbed-oxygen covered surface of AlOx tunnel barrier layers. These states change when chemisorbed oxygen ions are moved into the oxide by either flood gun electron bombardment or by thermal annealing. The former, if sufficiently energetic, results in locally well defined conduction band onsets at ~1 V, while the latter results in a progressively higher local conduction band onset, exceeding 2.3 V for 500 and 600 C thermal anneals.