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.