Abstract
The evolution of the electron band structure upon the reduction of Sb film on a Si(111)-(6 × 6)Au substrate, relevant to topological insulator properties, is experimentally systematically investigated by the reflection high-energy electron diffraction (RHEED), in situ surface electron transport and angular resolved photoemission spectroscopy methods. The experiments reveal that a bilayer (BL) of Sb is crystalline but the subsequent three BLs on top of it form amorphous layers. The five-BL-thick film transforms back to the crystalline form. The bilayer as well as 1.2- and 3.8-BL-thick films show the electron band structure with a relatively large energy gap at the Γ point of the Brillouin zone. The theoretically predicted band structure is observed at 4.8 BL coverage.
Highlights
Two surface bands of elemental antimony are connected to the conduction band and the valence band separately
The first-principles calculations have predicted the surface-coupling–induced gap in four and five-BL films [5]. Another theoretical work [6] has studied this problem and came to similar conclusions, i.e., the free-standing ultra-thin Sb films with a preserved, relaxed, crystal structure should undergo the transition from a simple wide-band-gap material to a topological insulator phase for films with thicknesses between four and eight BLs, and to ordinary semi-metal
In the present paper we report on the reflection high-energy electron diffraction (RHEED), the angular resolved photoemission electron spectroscopy (ARPES), and the in situ electric surface resistance variation study of Sb films on the Si(111)-(6 × 6)Au surface
Summary
Two surface bands of elemental antimony are connected to the conduction band and the valence band separately. The bulk antimony crystal is semi-metallic, it is believed that in the form of ultra-thin film, it should acquire topological insulator properties [3]. First-principles calculations suggest that the topologically nontrivial insulating phase can be induced by tensile strain, pointing to the possibility of realizing the quantum Hall state for Sb thin films on proper substrates [4]. The first-principles calculations have predicted the surface-coupling–induced gap in four and five-BL films [5] Another theoretical work [6] has studied this problem and came to similar conclusions, i.e., the free-standing ultra-thin Sb films with a preserved, relaxed, crystal structure should undergo the transition from a simple wide-band-gap material (one BL thick) to a topological insulator phase for films with thicknesses between four and eight BLs, and to ordinary semi-metal. The observed modifications of the band structure of Sb(111) support existing theoretical predictions [3,4,5,6]
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