Investigating and Manipulating the Molecular Beam Epitaxy Growth Kinetics of Intrinsic Magnetic Topological Insulator MnBi2Te4 with in Situ Angle-Resolved Photoemission Spectroscopy

Intrinsic magnetic topological insulator MnBi2Te4 is the key to realizing the quantum anomalous Hall effect and other related quantum phenomena at a sufficiently high temperature for their practical electronic applications. The research progress on the novel material, however, is severely hindered by the extreme difficulty in preparing its high-quality thin films with well-controlled composition and thickness. Combining molecular beam epitaxy (MBE) and in situ angle-resolved photoemission spectroscopy (ARPES), we have systematically studied the growth conditions and kinetics of MnBi2Te4 thin films prepared by simple co-evaporation of Mn, Bi and Te. The transition and competition between the Mn-doped Bi2Te3 and MnBi2Te4 phases under different growth conditions have been mapped in detail, which gives the recipe and principles of growing high-quality MnBi2Te4 thin films. Particularly, to obtain high quality MnBi2Te4 films, it is crucial to raise the growth temperature as high as allowed by the nucleation of the films to minimize density of Mn substitutional atoms on Bi sites. The ARPES data also map the kinetic process in the nucleation and ripening of MnBi2Te4 islands. These results offer the essential information for designing and optimizing the MBE growth procedure of MnBi2Te4-like compounds to achieve the exotic topological quantum effects.