Twist-angle modulation of exciton absorption in MoS2/graphene heterojunctions

Abstract

The twist-angle dependence of exciton absorption in a molybdenum disulfide (MoS2)/graphene heterostructure (MGH) is reported. Using photoluminescence (PL) spectroscopy, we found that, as the twist angle increased, the MGH demonstrated an enhancement of PL intensity and a peak position blueshift, indicating that the exciton radiative recombination was positively correlated with the twist angle. In addition, optical reflectance measurements were performed in order to investigate the exciton absorption in the MGH. It was found that the reflectance of MGH samples was twist-angle dependent at wavelengths of 620 and 670 nm, which corresponds to the PL peak positions of MoS2. This was attributed to the change in interlayer charge transfer for different twist angles. Our findings confirm the tunability of the electronic structure in MGHs via the interlayer twist, which enriches our understanding of interlayer coupling and is important for the future development of electronic and optoelectronic devices based on 2D material heterostructures.

Developing Graphene‐Based Moiré Heterostructures for Twistronics

“…Correspondingly, the exciton formation process was promoted to facilitate exciton absorption, owing to the decreasing interlayer electron transfer (Figure 14e), where a wavelength of 620 nm corresponded to the photoluminescence peak of MoS 2 . [29] Additionally, the exciton lifetimes also exhibited a significant difference when the stacking order of graphene and TMDCs was varied. From transient absorption spectroscopy, the exciton lifetime of the WSe 2 /graphene heterostructure (Figure 14f) was considerably higher than that of the graphene/WSe 2 heterostructure (Figure 14g), owing to the difference in charge screening of the substrate.…”

“…[ 185 ] Moreover, the exciton effect also appeared in the graphene/TMDCs, such as graphene/MoS 2 , which showed that the exciton absorption is dependent on the twist angle. [ 29 ] As the twist angle increased, the interlayer coupling declined. Correspondingly, the exciton formation process was promoted to facilitate exciton absorption, owing to the decreasing interlayer electron transfer (Figure 14e ), where a wavelength of 620 nm corresponded to the photoluminescence peak of MoS 2 .…”

“…In addition to the preparation of graphene‐based moiré heterostructures, many recent studies focused on the observation of their topological and correlated properties, such as, the existence of a moiré superlattice and topological minibands, [ 10 , 17 , 23 , 24 , 25 ] the quantum anomalous Hall effect in twisted bilayer graphene (tBLG), [ 26 ] the Mott insulator in ABC‐TLG, [ 24 ] the ferromagnetism in tDBG, [ 16 ] the Pomeranchuk effect in MATBG, [ 27 ] the ferroelectricity in BLG/ h ‐BN, [ 28 ] and the exciton effect in graphene/TMDCs heterostructures. [ 29 ] A few reviews on the physical properties and applications have been reported; however, they are primarily focused on tBLG and TMDCs vdW heterostructures. [ 30 , 31 , 32 , 33 ] Currently, there was no review on the systematic description of moiré patterns appearing in heterostructures.…”

“…e) Reflectance spectra of the graphene/MoS 2 graphene heterostructure with different twist angles. Reproduced with permission [29]. Copyright 2019, AIP Publishing.…”

Investigação >i<ab initio>/i< dos mecanismos de formação de nanoflocos de dicalcogenetos de metais de transição

“…[109,110] De fato, observa-se que heterojunções formadas por MoS 2 /Gr com band-gap na região do espectro visível apresentam grande condutividade eletrônica, candidatando estes materiais híbridos para o uso em dispositivos fotovoltaicos. [111,112] Ademais, heterojunções MoS 2 /Gr encontram usos em sensores, [113,114] além do fato que a variação de hibridizações relativas, de acordo com o ângulo de rotação entre as monocamadas, produzirem comportamentos condutivos específicos (área que é conhecida como twistronics). [115,116] Os métodos mais utilizados atualmente para a síntese de heteroestruturas verticais MoS 2 /Gr, como a CVD, provêm materiais de alta qualidade e escaláveis.…”