Formation of a stable surface oxide in MnBi${}_2$Te${}_4$ thin films

Abstract

Understanding the air-stability of MnBi${}_2$Te${}_4$ thin films is crucial for the development and long-term operation of electronic devices based around magnetic topological insulators. In the present work, we study MnBi${}_2$Te${}_4$ thin films upon exposure to atmosphere using a combination of synchrotron-based photoelectron spectroscopy, room temperature electrical transport and atomic force microscopy to determine the oxidation process. After 2 days air exposure a 2 nm thick oxide passivates the surface, corresponding to oxidation of only the top two surface layers, with the underlying layers preserved. This protective oxide layer results in samples that still exhibit metallic conduction even after several days air exposure. Furthermore, the work function decreases from 4.4 eV for pristine MnBi${}_2$Te${}_4$ to 4.0 eV after the formation of the oxide, along with only a small shift in the core levels indicating minimal doping as a result of air exposure. With the oxide confined to the top surface layers, and the underlying layers preserved, it may be possible to explore new avenues in how to handle, prepare and passivate future MnBi${}_2$Te${}_4$ devices.

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Cited by in corpus (6)

• Fabrication-induced even-odd discrepancy of magnetotransport in few-layer MnBi${}_2$Te${}_4$
• Proximity-induced superconducting gap in the intrinsic magnetic topological insulator MnBi2Te4
• Hall-effect in the MnBi_2Te_4 crystal using silicon nitride nanomembrane via contacts
• Electrostatic effects of the MnBi2Te4-superconductor hetero-structures in chiral Majorana search
• Reactivity of ultra-thin Kagome Metal FeSn towards Oxygen and Water
• Strongly enhanced topological quantum phases in dual-surface AlO${}_x$-encapsulated MnBi${}_2$Te${}_4$