Abstract
A stable BiI3 monosheet has been grown for the first time on the (0001) surface of the topological insulator Bi2Se3 as confirmed by scanning tunnelling microscopy, surface X-ray diffraction, and X-ray photoemision spectroscopy. BiI3 is deposited by molecular beam epitaxy from the crystalline BiTeI precursor that undergoes decomposition sublimation. The key fragment of the bulk BiI3 structure, {{rm{a}}}_{infty }^{2}[I—Bi—I] layer of edge-sharing BiI6 octahedra, is preserved in the ultra-thin film limit, but exhibits large atomic relaxations. The stacking sequence of the trilayers and alternations of the Bi—I distances in the monosheet are the same as in the bulk BiI3 structure. Momentum resolved photoemission spectroscopy indicates a direct band gap of 1.2 eV. The Dirac surface state is completely destroyed and a new flat band appears in the band gap of the BiI3 film that could be interpreted as an interface state.
Highlights
Two-dimensional (2D) metal halides have been of interest since a long time for their intriguing and tunable properties
A stoichiometrically almost exact BiI3 film is deposited by decomposition sublimation of BiTeI, as corroborated by X-ray photoemission spectroscopy (XPS), scanning tunnelling microscopy (STM) and surface X-ray diffraction (SXRD)
BiI3 was molecular beam epitaxy (MBE)-deposited onto the substrate that was kept at room temperature
Summary
Two-dimensional (2D) metal halides have been of interest since a long time for their intriguing and tunable properties. We establish a different approach by depositing a monosheet of BiI3 on the (0001) surface of the topological insulator (TI) Bi2Se3 by using molecular beam epitaxy (MBE) from a Knudsen cell filled with presynthesized BiTeI single crystals heated to 380 °C. A stoichiometrically almost exact BiI3 film is deposited by decomposition sublimation of BiTeI, as corroborated by X-ray photoemission spectroscopy (XPS), scanning tunnelling microscopy (STM) and surface X-ray diffraction (SXRD).
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