Atomically smooth ultrathin films of topological insulator Sb2Te3

Abstract

The growth and characterization of single-crystalline thin films of topological insulators (TIs) is an important step towards their possible applications. Using in situ scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES), we show that moderately thick Sb 2 Te 3 films grown layer-by-layer by molecular beam epitaxy (MBE) on Si(111) are atomically smooth, single-crystalline, and intrinsically insulating. Furthermore, these films were found to exhibit a robust TI electronic structure with their Fermi energy lying within the energy gap of the bulk that intersects only the Dirac cone of the surface states. Depositing Cs in situ moves the Fermi energy of the Sb 2 Te 3 films without changing the electronic band structure, as predicted by theory. We found that the TI behavior is preserved in Sb 2 Te 3 films down to five quintuple layers (QLs).

Evolution of the topologically protected surface states in superconductorβ-Bi2Pd from the three-dimensional to the two-dimensional limit

“…In Table II, we list the gap values at the DP for all slabs considered. The thickness-dependent behavior of the gap at the DP found here is similar to the behavior observed in typical 3D topological insulators [55][56][57][73][74][75].…”

Quantum anomalous Hall effect in time-reversal-symmetry breaking topological insulators

“…Bi 2 Te 3 and Sb 2 Te 3 belong to the same space group and share very close lattice constants [24]. Beyond that, Bi 2 Te 3 is intrinsically n-type owing to the presence of Te vacancies [44], while Sb 2 Te 3 is generally p-type due to antisite defects [45]. Inspired by the idea of energy band engineering in conventional semiconducting (Al,Ga)As [67] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 25 the Dirac point.…”

“…From previous ARPES measurements [66,91] and first principles calculations [24,45], it is known that the surface Dirac cones are far away from the bulk conduction band bottom and quite close to the valence band. For our magnetic TI system, the energy spectrum is schematically shown in Fig.…”

Bifurcation of the edge-state width in a two-dimensional topological insulator

“…Epitaxially grown thin films of Bi 2 Se 3 showed weak antilocalization effects with large magnetic field, which represents the surface state of TI. [21] Nonetheless, the reduction in the sample size inevitably induces a gap in the metallic dispersion of TI due to the overlap of the surface states at the two opposite surfaces [22,23], which requires a detailed study of the surface or edge states. In 2D TI, some existing works have been performed on the properties of edge states [13,24].…”

“…When ξ is comparable to the sample width, the overlap of the edge states on the opposite boundaries becomes significant and develops a finite gap in the edge-state dispersions. Such effects have already been investigated by the variation of the film thickness [22,23].…”