Direct Growth of van der Waals Tin Diiodide Monolayers

Abstract

Two-dimensional (2D) van der Waals (vdW) materials have garnered considerable attention for their unique properties and potentials in a wide range of fields, which include nano-electronics/optoelectronics, solar energy, and catalysis. Meanwhile, challenges in the approaches toward achieving high-performance devices still inspire the search for new 2D vdW materials with precious properties. In this study, via molecular beam epitaxy, for the first time, the vdW SnI 2 monolayer is successfully fabricated with a new structure. Scanning tunneling microscopy/spectroscopy characterization, as corroborated by the density functional theory calculation, indicates that this SnI 2 monolayer exhibits a band gap of ≈2.9 eV in the visible purple range, and an indirect-to direct-band gap transition occurs in the SnI 2 bilayer. This study provides a new semiconducting 2D material that is promising as a building block in future electronics/optoelectronics.

Anisotropic properties of two-dimensional (2D) tin dihalide (SnX2, X = Cl, Br, I) monolayer binary materials

“…It is justified with DOS shown in figure 2(f). The obtained band gap in SnI 2 monolayer is comparable to the theoretical and experimental results [45,47]. Also, our DFT calculations show that all these SnDH monolayer binary materials are indirect band gap semiconducting materials.…”

“…It is also a good light absorber for solar cells [46]. The SnI 2 monolayer was recently successfully synthesized using the molecular beam epitaxy technique [47]. These halide materials also crystallize in p2 1/m and p 31/m space group and are less explored for their various physical properties.…”

Thermoelectric performance of XI 2 (X = Ge, Sn, Pb) bilayers

“…Although the experimental results for the TE performance have not been reported so far, low thermal conductivity of PbI 2 has been experimentally measured [43] and 2D SnI 2 down to the monolayer has also been successfully prepared in experiment recently. [60] These encouraging experimental progresses supply a reasonable prospect of the applications for 2D XI 2 in TE materials. Our finding of the difference between the monolayer and bilayer for the doping type with superior figure of merit and the in-plane anisotropy indicates that the inter-layer interaction plays an important role in the TE performance of XI 2 .…”

Surface Structures of CsSnI3(001) Films on Au(111)

“…21 Figure 1d is the height profile acquired at the smooth surface along the red broken line in Figure 1b, which indicates that the lattice constant of the hexagonal structure is about 0.45 nm, consistent with that of SnI 2 films. 24 Considering that bulk CsI has a body-centered cubic structure, the hexagonal structure may be assigned to remnant SnI 2 . Additionally, after further annealing the sample at 353 K, the remnant SnI 2 with the hexagonal structure seems to transform into SnI 6 octahedrons as a precursor of perovskite [Figure S1b].…”

“…Therefore, the surfaces with scattered protrusions should be assigned to the same terminated layers (Cs–I or Sn–I) Figure d is the height profile acquired at the smooth surface along the red broken line in Figure b, which indicates that the lattice constant of the hexagonal structure is about 0.45 nm, consistent with that of SnI 2 films . Considering that bulk CsI has a body-centered cubic structure, the hexagonal structure may be assigned to remnant SnI 2 .…”