Fig. 1.

Bi₂Se₃ film properties. a AFM image of a 10-QL Bi₂Se₃ film with a roughness of ~0.5 nm. 1 QL (≈1 nm) step of crystal terrace along the blue line is clearly observed. The white scale bar is 100 nm. b Bi₂Se₃ thickness-dependent resistivity, ρ _BiSe, and sheet carrier concentration, n _2D, in Bi₂Se₃ at room temperature. c, d ρ _BiSe and n _2D as a function of temperature for Bi₂Se₃ films with different thicknesses, respectively