Enhanced Light Absorption and Efficient Carrier Collection in MoS2 Monolayers on Au Nanopillars

We fabricated hybrid nanostructures consisting of MoS2 monolayers and Au nanopillar (Au-NP) arrays. The surface morphology and Raman spectra showed that the MoS2 flakes transferred onto the Au-NPs were very flat and nonstrained. The Raman and photoluminescence intensities of MoS2/Au-NP were 3- and 20-fold larger than those of MoS2 flakes on a flat Au thin film, respectively. The finite-difference time-domain calculations showed that the Au-NPs significantly concentrated the incident light near their surfaces, leading to broadband absorption enhancement in the MoS2 flakes. Compared with a flat Au thin film, the Au-NPs enabled a 6-fold increase in the absorption in the MoS2 monolayer at a wavelength of 615 nm. The contact potential difference mapping showed that the electric potential at the MoS2/Au contact region was higher than that of the suspended MoS2 region by 85 mV. Such potential modulation enabled the Au-NPs to efficiently collect photogenerated electrons from the MoS2 flakes, as revealed by the uniform positive surface photovoltage signals throughout the MoS2 surface.

Automated summary

Hybrid nanostructures of MoS2 monolayers and Au nanopillar arrays were fabricated. The MoS2 flakes transferred onto the Au-NPs were observed to be flat and nonstrained. The Raman and photoluminescence intensities of MoS2/Au-NP were significantly higher than those of MoS2 flakes on a flat Au thin film. Finite-difference time-domain calculations showed that the Au-NPs enhanced the absorption in the MoS2 flakes and enabled efficient collection of photogenerated electrons.