May 24, 2017 | 11:00 / Mühüm hadisələr
Using surface x-ray diffraction and scanning tunneling microscopy in combination with first-principles calculations, we have studied the geometric and electronic structure of Cs-deposited Bi2Se3 (0001) surface kept at room temperature. Two samples were investigated: a single Bi2Se3 crystal, whose surface was Ar sputtered and then annealed at ∼500 ◦C for several minutes prior to Cs deposition, and a 13-nm-thick epitaxial Bi2Se3 film that was not subject to sputtering and was annealed only at ∼350 ◦C. In the first case, a considerable fraction of Cs atoms occupy top layer Se atoms sites both on the terraces and along the upper step edges where they form one-dimensional-like structures parallel to the step. In the second case, Cs atoms occupy the f cc hollow site positions. First-principles calculations reveal that Cs atoms prefer to occupy Se positions on the Bi2Se3(0001) surface only if vacancies are present, which might be created during the crystal growth or during the surface preparation process. Otherwise, Cs atoms prefer to be located in f cc hollow sites in agreement with the experimental finding for the MBE-grown sample.
“Geometric and electronic structure of the Cs-doped Bi2Se3(0001) surface” M. M. Otrokov, A. Ernst, K. Mohseni, H. Fulara, S. Roy, G. R. Castro, J. Rubio-Zuazo, A. G. Ryabishchenkova, K. A. Kokh, O. E. Tereshchenko, Z. S. Aliev, M. B. Babanly, E. V. Chulkov, H. L. Meyerheim, and S. S. P. Parkin. “PHYSICAL REVIEW” B 95, 205429 (2017).