Spectroscopic evaluation of charge-transfer doping and strain in graphene/ MoS2 heterostructures

Abstract

It is important to study the van der Waals interface in emerging vertical heterostructures based on layered two-dimensional (2D) materials. Being atomically thin, 2D materials are susceptible to significant strains as well as charge transfer doping across the interfaces.Here we use Raman and photoluminescence (PL) spectroscopy to study the interface between monolayer graphene/MoS2 heterostructures prepared by mechanical exfoliation and layer-by-layer transfer. By using correlation analysis between the Raman modes of graphene and MoS2 we show that both layers are subjected to compressive strain and charge transfer doping following mechanical exfoliation and thermal annealing.Furthermore, we show that both strain and carrier concentration can be modulated in the Compression Compression Compression Compression Gains e -

Strain, Doping, and Electronic Transport of Large Area Monolayer MoS2 Exfoliated on Gold and Transferred to an Insulating Substrate

“…46−50 More recently such a method has been adopted by some authors also for 1L MoS 2 . 40,41,51 In Figure 3a, the black open circles represent the A 1 ′ vs E′ pairs for all the Raman spectra collected on 1L MoS 2 on Au, while the blue open triangles represent the data pairs for 1L MoS 2 on Al 2 O 3 . The red and black lines represent the theoretical relations between the frequencies of the two vibrational modes at a laser wavelength of 532 nm in the ideal cases of a purely strained (strain line) and of a purely doped (doping line) 1L MoS 2 .…”

Dissolution-precipitation growth of uniform and clean two dimensional transition metal dichalcogenides

“…We noticed that for an individual MoS 2 flake on molten glass, (i) the Raman spectrum showed an E 2g at 385.2 cm −1 and an A 1g at 402.8 cm −1 with a difference of 17.6 cm −1 , smaller than that of monolayer MoS 2 grown on a SiO 2 /Si substrate, (ii) the A exciton peak located at 686.8 nm showed a red shift compared with MoS 2 grown on a SiO 2 /Si substrate. These changes may be ascribed to a strain effect and dielectric screening between the monolayer MoS 2 and molten glass [ 33–35 ], since after the flake was transferred onto a SiO 2 /Si substrate, the Raman peaks and A exciton of DP-grown MoS 2 are similar to those of exfoliated monolayer ones (Figs S12 and S13). To sum up, the above results indicate that the MoS 2 grown using the DP method is a uniform monolayer.…”

Optical Inspection of 2D Materials: From Mechanical Exfoliation to Wafer‐Scale Growth and Beyond

“…PL spectra of the MoS 2 before and after assembling these two heterostructures (not shown here) also suggested the effects of compressive strain and hole doping in the MoS 2 , matching well the Raman spectral characteristics in Figure 8a. [224] One emerging group of vdW integrations is based on band alignment of individual semiconducting 2D materials, thereby allowing interlayer transitions or transfers (depending on the type of band alignment, as discussed below) between them, such that these vdW heterostructures are potentially useful in field of optoelectronics. Typically, two types of band alignment are possible, depending on the work functions of the component 2D materials.…”

“…a) Correlation analysis of Raman spectral peak positions of graphene (𝜔 G , G band; 𝜔 G' , 2D band; left panel) and MoS 2 (𝜔 A' , A 1g mode; 𝜔 E' , E 12g mode; right panel) before (blue) and after (red) vdW integration. Reproduced with permission [224]. Copyright 2019, American Physical Society.…”