In-Plane Anisotropic Faceting of Ultralarge and Thin Single-Crystalline Colloidal SnS Nanosheets

Abstract

The colloidal synthesis of large thin two-dimensional (2D) nanosheets is fascinating but challenging, since the growth along the lateral and vertical dimensions need to be controlled independently. In-plane anisotropy in 2D nanosheets is attracting more attention as well. We present a new synthesis for large colloidal single-crystalline SnS nanosheets with the thicknesses down to 7 nm and lateral sizes up to 8 µm. The synthesis uses trioctylphosphine-S (TOP-S) as sulfur source and oleic acid (with or without TOP) as ligands. Upon adjusting the capping ligand amount, the growth direction can be switched between anisotropic directions (armchair and zigzag) and isotropic directions ("ladder" directions), leading to an edge-morphology anisotropy. This is the first report on solution-phase synthesis of large thin SnS NSs with tunable edge faceting. Furthermore, electronic transport measurements show strong dependency on the crystallographic directions confirming structural anisotropy.

Recent Advances in 2D Metal Monochalcogenides

“…This method comprises hot injection, one-pot synthesis, hydrothermal intercalation, and sequential deposition. [4,61,126,182,183] As a fast and low-cost method for producing nanomaterials for largescale industrial application, the WCS of MMCs nanosheets has drawn attention recently to produce SnS, SnSe, GeS and GeSe nanosheets. [150,184] In a typical wet synthesis of colloidal MMC nanosheets using the hot injection method, the group IV elements, such as SnCl 2 , SnCl 4 , and Ge 4 , are used as an inorganic halide metal source.…”

Anisotropic circular photogalvanic effect in colloidal tin sulfide nanosheets

“…[14][15][16][17] With this method, it is possible to reduce the thickness to less than 10 nm, while the lateral dimensions of such crystals are large enough for contacting them with standard lithographic methods. 3,5,10,18 This allows to further investigate the novel properties of this semiconductor, such as the circular photogalvanic effect (CPGE). Based on the bulk inversion asymmetry (BIA) or the structural inversion asymmetry (SIA) of certain crystals, this effect results in a helicity dependent current at zero volt bias, when the crystal is illuminated with circularly polarized light.…”

“…Colloidal SnS nanosheets with a lateral size of up to 5 µm and a thickness of less than 10 nm (∼15 layers 11 ) have been synthesized based on the recipe, mentioned in our previous report. 18 Fig. 1a shows a transmission-electron microscope (TEM) image of the nanosheets, which were employed for our measurements.…”

“…The anisotropic growth of the nanosheets (faster growth along the zigzag direction) guarantees the relation between the dimensions of the sheets and their crystallographic directions. 3,18 A schematic of such a device is shown in Fig. 1b.…”

SnS Nanosheets for 105th Harmonic Soliton Molecule Generation

“…The interlayer of SnS is composed of alternating covalent bonding double layers of Sn and S atoms, while the weak van der Waals force interacts between layers. SnS has an adjustable band gap, the indirect band gap is about 1.0–1.35 eV and the direct band gap is about 1.3–1.6 eV, which indicates that SnS has great potential as a saturable absorber.Due to the existence of Sn vacancies in SnS, the conductive type of SnS is generally p‐type with a large intrinsic hole concentration of 10 17 cm −3 . The strong anisotropy of single‐layer SnS makes it have great piezoelectric, ferroelectric, and ferroelastic properties .…”