Abstract:Tin monosulfide (SnS) is a layered two-dimensional semiconductor that has attracted attention because of its potential applications, for instance, photovoltaics, optoelectronics, and valleytronics. However, these applications require synthesis of SnS flakes with a controlled thickness and shape. Here, we demonstrate the possibility of using Au nanoparticles to seed the nucleation, determine the position, and control the thickness of the growing SnS plates. Further, we use in situ transmission electron microsco… Show more
“…2d, e). This domain shape is consistent with a recent analysis of kinetic growth shapes of thin SnS flakes 44 .Fig. 2AFM of single-crystalline SnS 2 and ultrathin SnS/SnS 2 .…”
Vertical van der Waals (vdW) heterostructures of 2D crystals with defined interlayer twist are of interest for band-structure engineering via twist moiré superlattice potentials. To date, twist-heterostructures have been realized by micromechanical stacking. Direct synthesis is hindered by the tendency toward equilibrium stacking without interlayer twist. Here, we demonstrate that growing a 2D crystal with fixed azimuthal alignment to the substrate followed by transformation of this intermediate enables a potentially scalable synthesis of twisted heterostructures. Microscopy during growth of ultrathin orthorhombic SnS on trigonal SnS2 shows that vdW epitaxy yields azimuthal order even for non-isotypic 2D crystals. Excess sulfur drives a spontaneous transformation of the few-layer SnS to SnS2, whose orientation – rotated 30° against the underlying SnS2 crystal – is defined by the SnS intermediate rather than the substrate. Preferential nucleation of additional SnS on such twisted domains repeats the process, promising the realization of complex twisted stacks by bottom-up synthesis.
“…2d, e). This domain shape is consistent with a recent analysis of kinetic growth shapes of thin SnS flakes 44 .Fig. 2AFM of single-crystalline SnS 2 and ultrathin SnS/SnS 2 .…”
Vertical van der Waals (vdW) heterostructures of 2D crystals with defined interlayer twist are of interest for band-structure engineering via twist moiré superlattice potentials. To date, twist-heterostructures have been realized by micromechanical stacking. Direct synthesis is hindered by the tendency toward equilibrium stacking without interlayer twist. Here, we demonstrate that growing a 2D crystal with fixed azimuthal alignment to the substrate followed by transformation of this intermediate enables a potentially scalable synthesis of twisted heterostructures. Microscopy during growth of ultrathin orthorhombic SnS on trigonal SnS2 shows that vdW epitaxy yields azimuthal order even for non-isotypic 2D crystals. Excess sulfur drives a spontaneous transformation of the few-layer SnS to SnS2, whose orientation – rotated 30° against the underlying SnS2 crystal – is defined by the SnS intermediate rather than the substrate. Preferential nucleation of additional SnS on such twisted domains repeats the process, promising the realization of complex twisted stacks by bottom-up synthesis.
“…The spontaneous formation of core–shell heterostructures in a one‐pot synthesis from a SnS precursor containing small amounts of more sulfur‐rich phases raises the question about the underlying growth mechanism. No metallic Sn is detectable in the samples, which rules out SnS decomposition during evaporation . Hence, we conclude that the minority SnS 2 precursor phase acts a source of excess sulfur, required for the SnS 2 shell to form.…”
mentioning
confidence: 63%
“…No metallic Sn is detectable in the samples, which rules out SnS decomposition during evaporation. [9] Hence, we conclude that the minority SnS 2 precursor phase acts a source of excess sulfur, [11] required for the SnS 2 shell to form. Due to the structural mismatch with the more sulfur-rich tin chalcogenides the fast-growing SnS core cannot incorporate the additional sulfur, which instead accumulates and causes the formation of a phase-separated, layered SnS 2 shell in the as-grown core-shell heterostructures.…”
Section: Layered Heterostructuresmentioning
confidence: 90%
“…Figure shows a structural analysis of these plates by transmission electron microscopy (TEM). The overall shape conforms to that typically found for SnS: Close to square footprint, bounded by a large (001) top facet and predominantly (110) and side facets, often with one set of diagonally opposing corners terminated by smaller (010) facets (Figure a). High‐resolution (HR) TEM and selected‐area electron diffraction confirm that the flakes consist primarily of monocrystalline SnS (Figure b).…”
Engineered heterostructures create new functionality by integrating dissimilar materials. Combining different 2D crystals naturally produces two distinct classes of heterostructures, vertical van der Waals (vdW) stacks or 2D sheets bonded laterally by covalent line interfaces. When joining thicker layered crystals, the arising structural and topological conflicts can result in more complex geometries. Phase separation during one‐pot synthesis of layered tin chalcogenides spontaneously creates core–shell structures in which large orthorhombic SnS crystals are enclosed in a wrap‐around shell of trigonal SnS2, forcing the coexistence of parallel vdW layering along with unconventional, orthogonally layered core–shell interfaces. Measurements of the optoelectronic properties establish anisotropic carrier separation near type II core–shell interfaces and extended long‐wavelength light harvesting via spatially indirect interfacial absorption, making multifunctional layered core–shell structures attractive for energy‐conversion applications.
“…Faster decomposition was observed along the [100] direction. [161] The phase transition from Pnma to Cmcm is a two-step process. This is considered the main factor contributing to the high ZT of SnSe.…”
2D materials based on main group element compounds have recently attracted significant attention because of their rich stoichiometric ratios and structure motifs. This review focuses on the phases in various 2D binary materials including III-VI, IV-VI, V-VI, III-V, IV-V, and V-V materials. Reducing 3D materials to 2D introduces confinement and surface effects as well as stabilizes unstable 3D phases in their 2D form. Their crystal structures, stability, preparation, and applications are summarized based on theoretical predictions and experimental explorations. Moreover, various properties of 2D materials, such as ferroelectric effect, anisotropic optical and electrical properties, ultralow thermal conductivity, and topological state are discussed. Finally, a few perspectives and an outlook are given to inspire readers toward exploring 2D materials with new phases and properties.
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