Topotactic Reaction of Mn with InSe To Form MnIn ₂ Se ₄

Topotaxy in van der Waals (vdW) systems has the prospect of a layer-by-layer transformation and thus the formation of sought-after vdW heterostructures. Of particular interest is the introduction of magnetic properties in semiconducting heterostructures. In this context, we examine the reaction of the semiconducting InSe with Mn to form MnIn2Se4, a material with magnetic ordering. The studies are performed on InSe single crystals, and the reactions are performed under ultrahigh vacuum by vapor deposition of Mn (and Se). The reaction products are characterized by a combination of X-ray photoemission spectroscopy, low-energy ion scattering, and scanning tunneling microscopy. Co-deposition of Mn and Se results in the transformation and roughening of the surface into In2Se3 and thus an undesired compositional change. Deposition of Mn by itself goes through different reactions with InSe. Initially, Mn extracts Se from InSe, liberating and desorbing indium from the surface and causing the formation of etch pits. Upon annealing, the selenized Mn then transforms into the desired MnIn2Se4 reaction products in small islands. This study reveals the reaction pathways for unconventional methods for the creation of van der Waals materials and heterostructures.