Controlled van der Waals Epitaxy of Monolayer MoS₂ Triangular Domains on Graphene

Abstract

Multilayered heterostructures of two-dimensional materials have recently attracted increased interest because of their unique electronic and optical properties. Here, we present chemical vapor deposition (CVD) growth of triangular crystals of monolayer MoS2 on single-crystalline hexagonal graphene domains which are also grown by CVD. We found that MoS2 grows selectively on the graphene domains rather than on the bare supporting SiO2 surface. Reflecting the heteroepitaxy of the growth process, the MoS2 domains grown on graphene present two preferred equivalent orientations. The interaction between the MoS2 and the graphene induced an upshift of the Raman G and 2D bands of the graphene, while significant photoluminescence quenching was observed for the monolayer MoS2. Furthermore, photoinduced current modulation along with an optical memory effect was demonstrated for the MoS2-graphene heterostructure. Our work highlights that heterostructures synthesized by CVD offer an effective interlayer van der Waals interaction which can be developed for large-area multilayer electronic and photonic devices.

All Chemical Vapor Deposition Synthesis and Intrinsic Bandgap Observation of MoS2/Graphene Heterostructures

“…[ 21 ] Alternatively, Ago et al demonstrated the van der Waals epitaxy of monolayer MoS 2 on transferred Gr domains (from Cu foils) on SiO 2 /Si by using MoO 3 and S precursors. [ 22 ] To avoid the Gr sample transfer, Zhang et al [ 23 ] and Huang et al [ 24 ] subsequently synthesized monolayer MoS 2 directly on the bulk state of Gr, mainly toward investigating the metallic edge state and bandgap tunability at the domain boundary of MoS 2 by employing scanning tunneling microscopy and spectroscopy (STM/STS). However, the effects of Gr on MoS 2 mainly regarding the bandgap tunability and doping effect, etc., still can not be resolved on these heterostructures systems.…”

Phosphorous doped p-type MoS2 polycrystalline thin films via direct sulfurization of Mo film

“…Therefore considerable efforts are required for scalable synthesis of p-type MoS 2 film to realize practical applications. To date, a direct growth method of MoS 2 thin films by chemical vapor deposition (CVD) via vapor-phase reaction of MoO 3 and sulfur (S) powders, [18][19][20][21] MoCl 5 and S powders, 22,23 and metal Mo films [24][25][26][27][28] in a CVD furnace have been demonstrated to overcome a large area film synthesis. Among them, the direct grown method of TMDs (e.g.…”

Recent Advances in Controlling Syntheses and Energy Related Applications of MX2 and MX2/Graphene Heterostructures

“…To resolve such issues, Tsuji et al, presented APCVD growth of triangular MoS 2 flakes on the APCVD-derived, single-crystalline monolayer hexagonal Gr domains transferred on SiO 2 /Si substrates. [60] They found that monolayer MoS 2 selectively nucleated on the Gr domains rather than on the bare supporting SiO 2 surfaces, thus indicating a heteroepitaxy growth mechanism. Meanwhile, the MoS 2 domains revealed two preferred equivalent orientations (SEM image in Figure 8b).…”

“…The photo-induced electron transfer from monolayer MoS 2 to Gr and the optical memory effect were also demonstrated in the MoS 2 /Gr vertical heterostructures. [60] Subsequently, Alem et al, reported the syntheses of nearly freestanding MX 2 /Gr heterostructures on Quantifoil TEM grids with ≈2 μm holes by the APCVD growth of monolayer MX 2 on transferred monolayer Gr (from Cu foils) (Figure 8c). [127] Notably, this work enabled the on-site investigation of the growth dynamics of MX 2 on Gr surfaces at an atomic resolution.…”

“…[54][55][56][57] More importantly, this MX 2 /Au foil is compatible with some practical applications like electrocatalytic hydrogen evolution reaction (HER). [46,48,53,57] Later on, the MX 2 /Gr vertical heterostructures was also constructed by chemical vapor deposition (CVD) approach, including direct growth of MoS 2 on as-grown CVD Gr on Cu foils by using (NH 4 ) 2 MoS 4 precursors, [58] van der Waals epitaxy of monolayer MoS 2 on transferred Gr domains (from Cu foils) on SiO 2 /Si, [59,60] and all-CVD syntheses of monolayer MoS 2 /Gr heterostructures directly on Au foils. [61] Density functional theory (DFT) calculations indicated that the Gibbs free energy of hydrogen adsorbed on Mo-terminated edges of MoS 2 was close to that of Pt, [62,63] which made MoS 2 a potential substitute of Pt in electrocatalytic HER due to its cost-effective and earth-abundant nature.…”