Figure 1

Schematic illustration on tuning the vertical location of the topological surface states (TSS) as a topological insulator (TI) is covered with a layer of conventional insulator (CI).
(a), TSS floating to the top of the CI. (b), Staying put at the CI/TI interface. (c), Diving into the TI. (d), The atomic structure of ZnM/Bi2Se3 (M = S, Se, Te). The red lines denote the TSS; the arrows indicate the resulting directions of the topological phase transition.