Understanding the air-stability of MnBi2Te4 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 MnBi2Te4 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 MnBi2Te4 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 MnBi2Te4 devices.
@article{arxiv.2110.02412,
title = {Formation of a stable surface oxide in MnBi$_2$Te$_4$ thin films},
author = {Golrokh Akhgar and Qile Li and Iolanda Di Bernardo and Chi Xuan Trang and Chang Liu and Julie Karel and Anton Tadich and Michael S. Fuhrer and Mark T. Edmonds},
journal= {arXiv preprint arXiv:2110.02412},
year = {2022}
}