Microstructure and transport properties of epitaxial topological insulator Bi₂Se₃ thin films grown on MgO (100), Cr₂O₃ (0001), and Al₂O₃ (0001) templates

We report the epitaxial integration of defect-induced room temperature ferromagnetic insulators, Cr₂O₃ and MgO, with topological insulators Bi₂Se₃ on c-sapphire substrate by pulsed laser deposition. The structural, magnetic, and magnetotransport properties of ∼15nm Bi₂Se₃ thin films are investigated on each template. The lattice misfits of Cr₂O₃/Bi₂Se₃ and MgO/Bi₂Se₃ are ∼16% and ∼39%, respectively, where the critical thickness for pseudomorphic growth is less than one monolayer. The insulating behavior is more pronounced due to the additional scattering of the surface states of the Bi₂Se₃ layer by interfacing with MgO and Cr₂O₃. The weak antilocalization effect from the surface states is clearly suppressed, accounting for the presence of magnetic bottom layers. This work demonstrates an effective way to study the emergence of a ferromagnetic phase in topological insulators by the magnetic proximity effect in Bi₂Se₃, a step toward unveiling their exotic properties.