Epitaxial Growth and Structural Properties of Bi(110) Thin Films on TiSe₂ Substrates

Abstract

We report the growth and structural properties of Bi thin films on TiSe2 substrates by using a low-temperature scanning tunneling microscope. Extended Bi(110) thin films are formed on the TiSe2 substrates and adopt a distorted black-phosphorus structure at room temperature (RT). The diagonal of the Bi(110) rectangular unit cell is parallel to the close-packed direction of the top-layer Se atoms of the TiSe2 substrates, resulting in the formation of a stripe-shaped commensurate moiré pattern with a periodicity of ∼38.5 Å at RT. Meanwhile, the charge density wave phase transition of the TiSe2 substrate and the different coefficients of thermal expansion of Bi(110) and TiSe2 lead to the formation of a quasi-hexagonal incommensurate moiré pattern with a periodicity of 14.5 Å at 77 K. In particular, the combination of domains with twisting angles of 30° or 60° results in the formation of various domain boundaries. Our work is very helpful for understanding and tuning the structural and electronic properties of epitaxial Bi(110) thin films.

Enhanced Berry Curvature Dipole and Persistent Spin Texture in the Bi(110) Monolayer

“…The Bi(110) monolayer crystallizes with a distorted phosphorene structure that belongs to the nonsymmorphic space group Pmn 2 1 , − containing several symmetry operations of glide planes and screw axes (see Table ). The optimized lattice constants are a = 4.90 Å and b = 4.59 Å, which agree well with the experimental − and theoretical ,, results reported. A notable structural feature is the finite out-of-plane buckling (Figure a), resulting from the vertical shift of the two centered Bi atoms.…”

“…A notable structural feature is the finite out-of-plane buckling (Figure 1a), resulting from the vertical shift of the two centered Bi atoms. This buckling, as confirmed by DFT calculation and experiment, is the key factor in determining its topological properties 21,22,24,25 and is sensitive to electron/hole doping (Figure S1). Figure 1b,c shows the calculated band structures of the flat and puckered Bi(110) structure, respectively.…”

Polymorphism in Post-Dichalcogenide Two-Dimensional Materials

“…The substrate dependence in the formation of this vdW aw-Bi structure in ultrathin bismuth films was further investigated by Kokubo et al, who found no explicit dependence on substrate symmetry. 285 The 2D aw-Bi structure has also been reported for the MBE growth of bismuth on NbTe 2 , 243,286 TaS 2 , 287 TiSe 2 , 288 and EG/SiC. 289 Furthermore, a report by Lu et al indicates that the degree of out-of-plane buckling in aw-Bi is dependent on the degree of charge transfer from the growth substrate.…”

Observation of Topological Edge States on α-Bi4Br4 Nanowires Grown on TiSe2 Substrates

“…Before the growth of α-Bi 4 Br 4 nanowires, the surface cleanness of the TiSe 2 crystals was checked with STM (Figure S1, Supporting Information). The α-Bi 4 Br 4 nanowires were grown on the TiSe 2 single crystals via a two-step process: In a first step, Bi was deposited on the TiSe 2 substrates at room temperature, leading to the formation Bi(110) thin films . The samples were then heated up to ∼470 K and exposed to the BiBr 3 flux.…”

“…The α-Bi 4 Br 4 nanowires were grown on the TiSe 2 single crystals via a two-step process: In a first step, Bi was deposited on the TiSe 2 substrates at room temperature, leading to the formation Bi(110) thin films. 44 The samples were then heated up to ∼470 K and exposed to the BiBr 3 flux. The typical deposition rate of Bi and BiBr 3 was ∼0.04 monolayer (ML)/min and 0.50 ML/min, as calibrated by LT-STM, respectively.…”