Search

MoS2 is promising for the next generation of electronic and optoelectronic devices by virtue of its unique optical, electrical and mechanical properties. Bandgap engineering of it is an interesting topic. However, the reported factors including temperature, defect, strain and external electric field are difficult to handle precisely. Here, we demonstrated direct–indirect bandgap transition in monolayer MoS2 induced by an individual Si nanoparticle. We observed photoluminescence (PL) emission with obvious spectral redshift and broadening in the MoS2/Si heterostructures after depositing Si nanoparticles onto the surface of monolayer MoS2. Raman spectra of heterostructures show measurable shifts in contrast with the bare MoS2. Energy transfer between MoS2 and Si nanoparticles did not happen, which is demonstrated by scattering spectra of MoS2/Si heterostructures. In addition, the natural oxide layer presented on the surface of Si nanoparticles can effectively prevent the carrier transferring from Si nanoparticles to MoS2. Thus, we attribute the direct–indirect bandgap transition of monolayer MoS2 to the strain induced by Si nanoparticles controlled by their sizes. The PL intensity of MoS2/Si heterostructure depends on the size of Si nanoparticles, resulting from the enhanced optical absorption of monolayer MoS2 based on Mie resonances of Si nanoparticles. The MoS2/Si heterostructure is promising for photodetector and circuit integration. [ABSTRACT FROM AUTHOR]

Abstract: Coupling between light and matter has many infusive physical effects and potential applications. Large Rabi splitting energy is achieved in many plasmonic nanostructures; however, these noble metallic materials generally suffer from a high level of Joule heating losses at optical frequencies. As an alternative strategy, all‐dielectric materials for manipulating light at the subwavelength scale have attracted enormous interest. However, the understanding of the interactions between all‐dielectric nanostructures and molecular excitons remains limited to date. Here, the use of a germanium nanogroove as a new all‐dielectric metasurface building block is demonstrated for the Kerker effect between molecular excitons and nanocavities. A distinct dip in the backward scattering spectra is observed, indicating relatively strong light–matter interaction due to the cavity magnetic resonance mode in the grooves. Germanium with a large real part and nonnegligible imaginary part of the refractive index in the visible region provides magnetic field enhancement similar to that of other all‐dielectric nanostructures; this phenomenon is theoretically explained by simulating the magnetic field distribution in the grooves. These findings may help researchers to better understand the interactions between all‐dielectric nanostructures and molecular excitons and indicate that germanium nanogrooves can potentially be used as metasurface building blocks in nanophotonic devices. [ABSTRACT FROM AUTHOR]

Strong Coulomb interactions in monolayer transition metal dichalcogenides (TMDs) produce strongly bound excitons, trions, and biexcitons. The existence of multiexcitonic states has drawn tremendous attention because of its promising applications in quantum information. Combining different monolayer TMDs into van der Waals (vdW) heterostructures opens up opportunities to engineer exciton devices and bring new phenomena. Spatially separated electrons and holes in different layers produce interlayer excitons. Although much progress has been made on excitons in single layers, how interlayer excitons contribute the photoluminescence emission and how to tailor the interlayer exciton emission have not been well understood. Here, room temperature strong coupling between interlayer excitons in the WS2/MoS2 vdW heterostructure and cavity‐enhanced Mie resonances in individual silicon nanoparticles (Si NPs) are demonstrated. The heterostructures are inserted into a Si film‐Si NP all‐dielectric platform to realize effective energy exchanges and Rabi oscillations. Besides mode splitting in scattering, tunable interlayer excitonic emission is also observed. The results make it possible to design TMDs heterostructures with various excitonic states for future photonics devices. [ABSTRACT FROM AUTHOR]

MoS 2 is promising for the next generation of electronic and optoelectronic devices by virtue of its unique optical, electrical and mechanical properties. Bandgap engineering of it is an interesting topic. However, the reported factors including temperature, defect, strain and external electric field are difficult to handle precisely. Here, we demonstrated direct-indirect bandgap transition in monolayer MoS 2 induced by an individual Si nanoparticle. We observed photoluminescence (PL) emission with obvious spectral redshift and broadening in the MoS 2 /Si heterostructures after depositing Si nanoparticles onto the surface of monolayer MoS 2 . Raman spectra of heterostructures show measurable shifts in contrast with the bare MoS 2 . Energy transfer between MoS 2 and Si nanoparticles did not happen, which is demonstrated by scattering spectra of MoS 2 /Si heterostructures. In addition, the natural oxide layer presented on the surface of Si nanoparticles can effectively prevent the carrier transferring from Si nanoparticles to MoS 2 . Thus, we attribute the direct-indirect bandgap transition of monolayer MoS 2 to the strain induced by Si nanoparticles controlled by their sizes. The PL intensity of MoS 2 /Si heterostructure depends on the size of Si nanoparticles, resulting from the enhanced optical absorption of monolayer MoS 2 based on Mie resonances of Si nanoparticles. The MoS 2 /Si heterostructure is promising for photodetector and circuit integration.

Strong Coulomb interactions in monolayer transition metal dichalcogenides (TMDs) produce strongly bound excitons, trions, and biexcitons. The existence of multiexcitonic states has drawn tremendous attention because of its promising applications in quantum information. Combining different monolayer TMDs into van der Waals (vdW) heterostructures opens up opportunities to engineer exciton devices and bring new phenomena. Spatially separated electrons and holes in different layers produce interlayer excitons. Although much progress has been made on excitons in single layers, how interlayer excitons contribute the photoluminescence emission and how to tailor the interlayer exciton emission have not been well understood. Here, room temperature strong coupling between interlayer excitons in the WS 2 /MoS 2 vdW heterostructure and cavity-enhanced Mie resonances in individual silicon nanoparticles (Si NPs) are demonstrated. The heterostructures are inserted into a Si film-Si NP all-dielectric platform to realize effective energy exchanges and Rabi oscillations. Besides mode splitting in scattering, tunable interlayer excitonic emission is also observed. The results make it possible to design TMDs heterostructures with various excitonic states for future photonics devices., Competing Interests: The authors declare no conflict of interest.