Overgrowth of Bi2Te3 nanoislands on Fe-based epitaxial ferromagnetic layers

Abstract

Bi₂Te₃ is deposited by hot wall epitaxy in an attempt to form nanosheets on epitaxially-grown ferromagnetic layers of Fe, Fe₃Si and Co₂FeSi. Bi₂Te₃ reacts strongly with pure Fe, producing FeTe₂. The reaction is suppressed for silicides Fe₃Si and Co₂FeSi. For the latter, partial incorporation of Co into the Bi₂Te₃ islands occurs at high temperatures, causing magnetic doping of the topological insulator. Although (0001) remains to be the favored growth orientation on Fe₃Si and Co₂FeSi, non-(0001)-oriented three-dimensional islands dominantly coexist on these surfaces further strengthening the growth characteristic on GaAs and contrary to the overwhelming formation of the nanosheets on Si and SiO₂. Deterioration of the magnetic properties of the ferromagnetic layers by heat treatment in the overgrowth is confirmed to be not significant. In addition, we show the surface plasmon emission in the visible energy range from the nanoislands. Finding the material combinations for which the overlayer-substrate reaction is circumvented opens the way to epitaxially create topological-insulator–ferromagnet multiple layer structures.