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Abstract Van der Waals (vdW) heterostructures that pair materials with diverse properties enable various quantum phenomena. However, the direct growth of vdW heterostructures is challenging. Modification of the surface layer of quantum materials to introduce new properties is an alternative process akin to solid state reaction. Here, vapor deposited transition metals (TMs), Cr and Mn, are reacted with Bi2Se3with the goal to transform the surface layer to XBi2Se4(X = Cr, Mn). Experiments and ab initio MD simulations demonstrate that the TMs have a high selenium affinity driving Se diffusion toward the TM. For monolayer Cr, the surface Bi2Se3is reduced to Bi2‐layer and a stable (pseudo) 2D Cr1+δSe2layer is formed. In contrast, monolayer Mn can transform upon mild annealing into MnBi2Se4. This phase only forms for a precise amount of initial Mn deposition. Sub‐monolayer amounts dissolve into the bulk, and multilayers form stable MnSe adlayers. This study highlights the delicate energy balance between adlayers and desired surface modified layers that governs the interface reactions and that the formation of stable adlayers can prevent the reaction with the substrate. The success of obtaining MnBi2Se4points toward an approach for the engineering of other multicomponent vdW materials by surface reactions.
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Alloying of Mn with Bi‐Rich Surfaces of Bi 2 Te 3 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 Bi2Te3as a platform to create novel 2D overlayers on the TI‐ substrate. Specifically, the Bi2layer 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 Bi2Te3surface 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.
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- Award ID(s):
- 2118414
- PAR ID:
- 10627776
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Small
- Volume:
- 21
- Issue:
- 39
- ISSN:
- 1613-6810
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/smll.202504498
