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

Abstract

ⓒ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 AuNRs