Two-step synthesis and characterization of vertically stacked SnS–WS₂ and SnS–MoS₂ p–n heterojunctions

Abstract

We demonstrate the synthesis of unique heterostructures consisting of SnS and WS (or SnS and MoS) by two-step chemical vapor deposition (CVD). After the first CVD growth of triangular WS (MoS) grains, the second CVD step was performed to grow square SnS grains on the same substrate. We found that these SnS grains can be grown at very low temperature with the substrate temperature of 200 °C. Most of the SnS grains nucleated from the side edges of WS (MoS) grains, resulting in the formation of partly stacked heterostructures with a large overlapping area. The SnS grains showed doped p-type transfer character with a hole mobility of 15 cm V s, while the WS and MoS grains displayed n-type character with a high on/off ratio of >10. The SnS-WS and SnS-MoS heterostructures exhibited clear rectifying behavior, signifying the formation of p-n junctions at their interfaces. This heterostructure growth combined with the low temperature SnS growth will provide a promising means to exploit two-dimensional heterostructures by avoiding possible damage to the first material.

Nanoparticle-Templated Thickness Controlled Growth, Thermal Stability, and Decomposition of Ultrathin Tin Sulfide Plates

“…The SnS flakes nucleate either at step edges of van der Waals substrates or randomly on flat substrate terraces, and are polydisperse and have a variety of thicknesses (typically multilayers exceeding 10–15 nm), and even on flat substrates such as mica are not all horizontal . Interestingly, the SnS flakes invariably exhibit faceted shapes bounded by the {110} side facets rather than the armchair and zigzag edges, ,− and the same types of faceted crystal shapes are observed for the isostructural and chemically similar SnSe . Crystal facets with a lower surface energy are expected to be part of the equilibrium (Wulff) shape that minimizes the total surface energy of a crystal.…”

“…11,12 To access the extraordinary properties predicted for mono-and few-layer SnS for applications, 13,14 the controlled synthesis of SnS with particular thickness and shapes needs to be developed. The growth of SnS plates by physical vapor deposition or vapor transport uses stoichiometric SnS powder 10,15,16 or a combination of SnO/SnO 2 and S 17,18 as source materials and yields different types of SnS flakes depending on the substrate used, that is, basal plane-oriented layered SnS crystals on flat and relatively inert supports such as graphite, graphene 19 or mica, 6,10,15,16 and vertical/standing SnS flakes on more reactive supports such as Si or SiO 2 . 19,20 Standing SnS flakes integrated in devices demonstrate very high response speeds for fast photodetection, several orders of magnitude higher than those of horizontal geometries.…”

“…SnS has attracted interest for light harvesting because of its suitable bandgap and large absorption coefficient (>10 4 cm –1 ), low cost, nontoxic, as well as anisotropic electronic, optical, thermal, and mechanical properties. , To access the extraordinary properties predicted for mono- and few-layer SnS for applications, , the controlled synthesis of SnS with particular thickness and shapes needs to be developed. The growth of SnS plates by physical vapor deposition or vapor transport uses stoichiometric SnS powder ,, or a combination of SnO/SnO 2 and S , as source materials and yields different types of SnS flakes depending on the substrate used, that is, basal plane-oriented layered SnS crystals on flat and relatively inert supports such as graphite, graphene or mica, ,,, and vertical/standing SnS flakes on more reactive supports such as Si or SiO 2 . , Standing SnS flakes integrated in devices demonstrate very high response speeds for fast photodetection, several orders of magnitude higher than those of horizontal geometries. , Devices such as IR photodetectors incorporating SnS sheets show excellent external quantum efficiency, which can be further enhanced by decoration with Au particles …”

Vertical Heterostructure of SnS–MoS2 Synthesized by Sulfur-Preloaded Chemical Vapor Deposition

“…Chemical vapor deposition (CVD) is a powerful approach to synthesize the HS of a vertically stacked 2D nanostructure. Currently, several pivotal CVD methods has been dedicated to vertical HS, for example, WS 2 /MoS 2 , VSe 2 /WSe 2 , ReS 2 /WS 2 , CdI 2 /MoS 2 (WS 2 , WSe 2 ) . However, the growth of vertically stacked 2D HS with large overlapping interfacial regions was usually limited to two components that have a small lattice mismatch.…”

“…For example, Sukma Aji et al. reported the synthesis of HS between SnS and WS 2 (or SnS and MoS 2 ) by two-step CVD . We have recently demonstrated that Cu 2– x S form into nanoparticles above the MoS 2 monolayer (ML) in CVD .…”