Growth of Bi₂Se₃/graphene heterostructures with the room temperature high carrier mobility

Heterostructures of Bi₂Se₃ topological insulators were epitaxially grown on graphene by means of the physical vapor deposition at 500 °C. Micrometer-sized flakes with thickness 1 QL (quintuple layer ~ 1 nm) and films of millimeter-scale with thicknesses 2–6 QL had been grown on CVD graphene. The minimum thickness of large-scaled continuous Bi₂Se₃ films was found to be ~ 8 QL for the regime used. The heterostructures with a Bi₂Se₃ film thickness of > 10 QL had resistivity as low as 200–500 Ω/sq and a high room temperature carrier mobility ~ 1000–3400 cm²/Vs in the Bi₂Se₃/graphene interface channel. Moreover, the coexistence of a p-type graphene-related conductive channel, simultaneously with the n-type conductive surface channel of Bi₂Se₃, was observed. The improvement of the bottom Bi₂Se₃/graphene interface with the increase in the growth time clearly manifested itself in the increase of conductivity and carrier mobility in the grown layer. The grown Bi₂Se₃/G structures have lower resistivities and more than one order of magnitude higher carrier mobilities in comparison with the van der Waals Bi₂Se₃/graphene heterostructures created employing exfoliation of thin Bi₂Se₃ layers. The grown heterostructures demonstrated the properties that are perspective for new functional devices, for a variety of signal processing and logic applications.