Trivial band topology of ultra-thin rhombohedral Sb2Se3 grown on Bi2Se3.

Thin films of rhombohedral Sb2Se3 with thicknesses from 1 to 5 quintuple layers (QL) were grown on Bi2Se3/Si(1 1 1) substrate. The electronic band structure of the grown films and the Sb2Se3/Bi2Se3 interface were studied using angle-resolved photoemission spectroscopy. It was found that while Sb2Se3 has an electronic band structure generally similar to that of Bi2Se3, there is no fingerprints of band inversion in it. Instead, the one-QL-thick Sb2Se3 films show direct band gap of about 80 meV. With growing film thickness, the Fermi level of the Sb2Se3 films gradually shifts by 200 meV for 5 QL-thick film revealing the band bending of the Sb2Se3/Bi2Se3 hetero-junction.