Investigating and manipulating the molecular beam epitaxy growth kinetics of intrinsic magnetic topological insulator MnBi ₂ Te ₄ with <i>in situ</i> angle-resolved photoemission spectroscopy

Abstract

Intrinsic magnetic topological insulator MnBi₂Te₄is 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<i>in situ</i>angle-resolved photoemission spectroscopy (ARPES), we have systematically studied the growth conditions and kinetics of MnBi₂Te₄thin films prepared by simple co-evaporation of Mn, Bi and Te. The transition and competition between the Mn-doped Bi₂Te₃and MnBi₂Te₄phases under different growth conditions have been mapped in detail, which gives the recipe and principles of growing high-quality MnBi₂Te₄thin films. Particularly, to obtain high quality MnBi₂Te₄films, 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 MnBi₂Te₄islands. 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.