Modulation of surface states in Sb₂Te₃/Bi₂Te₃ topological insulator heterostructures

The direct access of the topological surface states by electrical transport measurements is a necessary requirement for the implementation of the exceptional properties of topological insulators (TIs) in applications. In most TIs, however, the bulk is not insulating and the Dirac point is not exposed or not close to the Fermi level, masking the topological phenomena. Therefore, band structure engineering, e.g. by combining TI materials with complementary electronic properties, is in the focus of the research. Here we study the very promising approach of interfacing two TIs, namely Bi₂Te₃ and Sb₂Te₃. Heterostructures of Bi₂Te₃ thin films [1-3] with various thicknesses of the Sb₂Te₃ top layer are prepared by molecular beam epitaxy. Using in situ angle-resolved photoelectron spectroscopy, we are able to differentiate the modulation of the surface states from the shift of the chemical potential due to doping. Moreover, the interdiffusion at the interface of the TIs is studied and optimized by utilizing growth recipes involving different growth temperatures.
[1] V. M. Pereira et al., Phys. Rev. Materials 4, 064202 (2020)
[2] V. M. Pereira et al., APL Mater. 8, 071114 (2020)
[3] V. M. Pereira et al., Phys. Status Solidi B, 2000346 (2020)