Sub-Band-Gap Photoresponse Caused by Hot Electron Injections in Au Nanorod Decorated van der Waals Semiconductor Monolayers

ⓒ2020 The Korean Physical Society Hot electrons in metal nanostructures can be exploited in a wide range of optical functions, including photocatalysis, surface-enhanced Raman scattering, photodetectors and photovoltaics. Here, we report the sub-band-gap (E-g) photoresponse in Au-nanorod decorated van der Waals (vdW) semiconductor, MoS(2)and WSe2, monolayers (MLs). We found that hot electrons, optically excited in Au nanorod (NR) arrays at sub-E(g)radiations, can be injected intovdWML semiconductors over Schottky barriers, producing substantial photocurrents inn-type MoS(2)andp-type WSe2ML photodetectors, as well as photovoltages inn-MoS2/p-WSe2ML stack junctions. Moreover, by using spectrally and light-polarization resolved measurements, we showed that these sub-E(g)excitations of hot electrons can be modulated by tuning the plasmon resonance to the shape-controlled AuNRs11sciekc