Surface Termination of CleavedBi2Se3Investigated by Low Energy Ion Scattering

Abstract

It has been widely assumed that Se terminates the surface of the topological insulator, bismuth selenide. Although some Se is initially at the surface after cleaving at 80 K, low energy ion scattering reveals a complete Bi termination at room temperature. Density functional theory shows that a Bi bilayer atop the bulk-terminated structure is energetically favorable. It is thus proposed that a thermally activated process induces a spontaneous termination change after cleaving. This has profound implications on the electrical transport and long-term stability of such materials and devices.

Termination of single-crystal Bi2Se3 surfaces prepared by various methods

“…Note that this was the conclusion of ref. [12], although that paper reported that the resulting surface was Bi-terminated and not simply Bi-rich.…”

Communication: Surface stability and topological surface states of cleaved Bi2Se3: First-principles studies

“…2(c). 17 One may view this feature as the consequence of the topological protection of the Dirac state of Bi 2 Se 3 (111) surface upon Bi adsorption, similar with what occurs for the Bi bilayer on the Bi 2 Te 3 surface. [28][29][30][31] The single-particle Dirac spectra of +2Bi surface were observed experimentally with ARPES, together with a similar analysis on DFT bands.…”

“…15,16 Recent experiments of low energy ion scattering (LEIS) showed that a Bi bilayer forms on the Bi 2 Se 3 (111) surface after in situ cleavage at room temperature, a new mechanism for the "aging effect." 17 Experimental studies by Edmond et al also demonstrated the formation of isolated Bi bilayer at the vacuum-cleaved surface of Bi 2 Se 3 upon even brief exposure to atmosphere. 18 Interestingly, the Bi-rich termination may then undergo a "second" reconstruction and form a Bi 2 Se 3 terminated final state after 3-day air exposures.…”

“…The +2Bi model is more stable than the Gen in the Bi-rich condition, indicating that a Bi bilayer tends to cover the Gen surface. 17 The "adsorption energy" of a Bi (111) 26 Since STM senses the electron density rather than the positions of nuclei, we believe that the discrepancy between theory and experiment partially stems from the size difference between Bi and Se atoms. The QL + 2Bi + QL slab that has a Bi(111)-bilayer under the first QL is even lower in energy than the +2Bi surface.…”

Termination-dependent topological surface states of the natural superlattice phase Bi4Se3

“…For example, a basic understanding of the surface band structures of more complex topological materials, while highly desirable, is not trivial. Although there have been studies of different materials at the interface of 3D TIs, 16,17 and on different surface terminations of the same material, 18,19 no in-depth study of the TSS and electronic band structure of a complex topological material or a true bulk topological superlattice material has yet been reported.Here, we investigate the properties of Bi 4 Se 3 , the simplest topological superlattice material, consisting of single Bi 2 layers interleaved with single Bi 2 Se 3 layers in a 1:1 ratio 20 [ Fig. 1(a)].…”