Vertical Stacking of Copper Sulfide Nanoparticles and Molybdenum Sulfide Nanosheets for Enhanced Nonlinear Absorption

Abstract

The construction of p–n junctions is necessitated by applications which require effective charge separation. Here, a novel heterostructure (HS) of molybdenum sulfide (MoS2) and copper sulfide (Cu2–x S) was synthesized by chemical vapor deposition, with Cu2–x S nanoparticles vertically stacked on a MoS2 nanosheet. A well-defined epitaxial relationship between MoS2 and Cu2–x S is established, although the corresponding lattice mismatch is as large as 20%. The band-edge alignment is experimentally determined, indicating that the MoS2–Cu2–x S HS is a type II heterojunction. Photoluminescence quenching indicates effective charge separation in HS. The resultant HS shows enhanced nonlinear absorption in comparison with single-component MoS2 nanosheets and Cu2–x S nanoparticles.

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

“…The contrast spectrum of original MoS 2 and S–MoS 2 were measured by a microspectrophotometer; the experimental setup can be found in our previous report . The contrast difference between the Si/SiO 2 and MoS 2 regions was measured (Figure d).…”

“…X-ray photoelectron spectroscopy (XPS) experiment was carried out on a Kratos Axis Ultra DLD. Nonlinear response of materials was investigated on an individual-beam nonlinear transmittance setup, and more information can be found in our previous paper …”

“…Heterostructure (HS) plays important roles in opto-electronic devices (e.g., photovoltaics, photocatalysis, photodetector, light-emitting diode) relying on effective charge separation. − The advantage of HS is manifested at the interface between two components, where the band structure of each component is modulated so that the separation of photogenerated free carriers can be enhanced. − Vertically stacked two-dimensional (2D) HS with large overlapping regions is highly desirable because the larger interfacial area between two components is beneficial for charge separation. The HS is an idea candidate for high-performance nonlinear optical (NLO) materials because efficient charge delocalization is necessitated by NLO response (e.g., transition metal porphryins, porphyrin-modified graphene, Ag 2 Se–CdSe HS, and Cu 2– X S–MoS 2 HS). 2D nanostructures have a unique electronic structure, and therefore the research concerning NLO response of 2D nanostructures is attractive.…”

“…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 . The growth of vertically stacked 2D HS with larger overlapping regions between components with large lattice mismatch remains a big challenge.…”

Nanoengineering of Tin Monosulfide (SnS)‐Based Structures for Emerging Applications

“…[127] The schematic diagram of the fabrication procedure of 2D SnS NS/ 2D MoS 2 NS heterostructure is presented in Figure 8h. It has three steps: i) sulfurization of raw material MoO 3 was carried out to fabricate a MoS 2 monolayer on a SiO 2 /Si substrate [129,130] ; ii) the preferential adsorption of S on the MoS 2 monolayer; iii) S-preloaded MoS 2 was converted into the 2D SnS/2D MoS 2 vertical heterostructure after the flow of SnCl 4 vapor. Raman spectroscopy shows that the A 1g mode of the MoS 2 monolayer in the 2D SnS NS/2D MoS 2 NS heterostructure is slightly blue-shifted (Figure 8i), suggesting the p-type doping of the MoS 2 monolayer by 2D SnS NS.…”