Enhancement of the Surface Morphology of (Bi 0.4 Sb 0.6 ) 2 Te 3 Thin Films by In Situ Thermal Annealing.

The study of the exotic properties of the surface states of topological insulators requires defect-free and smooth surfaces. This work aims to study the enhancement of the surface morphology of optimally doped, high-crystalline (Bi 0.4 Sb 0.6 ) 2 Te 3 films deposited by molecular beam epitaxy on Al 2 O 3 (001) substrates. Atomic force microscopy shows that by employing an in situ thermal post anneal, the surface roughness is reduced significantly, and transmission electron microscopy reveals that structural defects are diminished substantially. Thence, these films provide a great platform for the research on the thickness-dependent properties of topological insulators.