Multilayer films composed of alternating layers of Bi and Se-Bi(4.55 A)/Se(6.82 A)_n (Bi4Se6), Bi(6.13 A)/SeCl2.26) A" (Bi6Sel2), and Bi(4.86 A)/Se(l8.46 A)" (Bi4Se18)-were fabricated by controlling the layer thickness at the atomic scale using thermal evaporation techniques. After annealing treatment, the Bi4Se 18 alternately layered film shows a single phase of BijSe3 rhombohedral crystalline structure with the characteristic density of single crystal Bi2Se3, whereas the Bi6Sel2 and Bi4Se6 films show locally disordered Bi2Se3 crystalline structure. The effectively controlled layeredstructure in the as-grown Bi4Sel8 film enhances the Bi-Se chemical bonding state. The formation of a layered crystalline structure during the annealing process increased as the thickness of Se increased. After interdifftision and the crystallization process, alternately layered Bi4SelS films become stable BijSe3 single crystals with a continuous and uniform layered structure. Finally, in the Bi-Se system, atomically controlled multilayers with an optimized ratio of each unit layer can be transformed to a perfect single-crystalline structure on oxidized Si with an amorphous phase through a self-organized ordering process.
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