Interfacial reactions at Fe/topological insulator spin contacts.

The authors study the composition and abruptness of the interfacial layers that form during deposition and patterning of a ferromagnet, Fe on a topological insulator (TI), Bi₂Se₃, Bi₂Te₃, and SiO_x/Bi₂Te₃. Such structures are potentially useful for spintronics. Cross-sectional transmission electron microscopy, including interfacial elemental mapping, confirms that Fe reacts with Bi₂Se₃ near room temperature, forming an abrupt 5 nm thick FeSe_0.92 single crystalline binary phase, predominantly (001) oriented, with lattice fringe spacing of 0.55 nm. In contrast, Fe/Bi₂Te₃ forms a polycrystalline Fe/TI interfacial alloy that can be prevented by the addition of an evaporated SiO_x separating Fe from the TI.