Alloying of Mn with Bi‐Rich Surfaces of Bi₂Te₃ by Topotactic Reaction

Abstract Interfacing topological insulators (TI) with magnetic materials enables accessing quantum effects for advanced devices. The synthesis of such heterostructures faces challenges due to interlaying mixing and the often‐complex multicomponent materials required to combine the desired properties. An alternative synthesis to direct growth is the modification of 2D materials by topotactic reactions to introduce new functionalities into pre‐formed single or few‐component 2D sheets. Here, the self‐formation of bismuthene (a bilayer of Bi; Bi₂) is utilized by thermal decomposition of Bi₂Te₃ as a platform to create novel 2D overlayers on the TI‐ substrate. Specifically, the Bi₂ layer is modified by reacting it with vapor deposited Mn in an attempt to induce magnetic properties. Scanning tunneling microscopy indicates that the Mn modified surface remains in a planar 2D layer, indicating the formation of an ordered Mn‐rich surface layer. Density functional theory (DFT) is used to develop models of both the Bi‐rich Bi₂Te₃ surface as well as their subsequent Mn‐modified structure. The DFT models indicate the possibility of magnetic ordering of the high spin Mn²⁺ ions. The successful synthesis of planar MnBi alloys on a van der Waals material illustrates topotactic reactions as an alternative for creating novel layered heterostructures.