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Stabilizing the Fermi Level of Cr-Doped Magnetic Topological Insulators by Al Passivation

Wu, Yu, Guo, Qixun, Zheng, Qi, Xu, Xiulan, Liu, Tao, Liu, Yang, Yan, Yu, Wang, Dongwei, Long, Shibing, Wang, Lijin, Yang, Shanwu, Teng, Jiao, Du, Shixuan, Yu, Guanghua
Journal of physical chemistry 2019 v.123 no.6 pp. 3823-3828
air, aluminum, bismuth, exposure duration, magnetism, physical chemistry, topology
The quantum anomalous Hall effect (QAHE) observed in magnetically doped topological insulators is not only fundamentally interesting but also has great potential applications such as quantum computation. To experimentally realize the QAHE, the Fermi level (EF) needs to be stabilized in the tiny surface-state gap. However, for topological insulators, even a very short time exposure to the atmosphere can induce a large EF shift. In this work, magnetic topological insulator Cr₀.₂₇(Bi₀.₄₃Sb₀.₆₃)₁.₇₃Te₃ (CBST) thin-films are successfully prepared via magnetron sputtering, which is a more universal, efficient, and affordable method for application. Then, the evolution of the EF position has been investigated as a function of the exposure time in the air through gate-dependent transport measurements. This study reveals that the EF position can be stabilized by in situ Al passivation with carrier doping significantly reduced, and the oxidations of Bi and Te atoms can also be suppressed. The availability of wide compositions for magnetron sputtering as well as the EF position stability of the in situ Al passivation may be a key for further investigations of the topological insulator toward the achievement of the QAHE in the sputtered CBST thin-film systems.