Plasmonic Silver Nanoparticle-Mediated Enhanced Broadband Photoresponse of Few-Layer Phosphorene/Si Vertical Heterojunctions.

We report the superior broadband photodetection characteristics of few-layer phosphorene known as black phosphorus (BP) nanosheets integrated with silver nanoparticles (Ag NPs) using vertical heterojunctions on a Si platform. The exfoliation of BP nanosheets and preparation of an Ag NP:BP (Ag-BP) hybrid have been accomplished through environment-friendly and cost-effective chemical routes. The hybrid sample exhibits broadband light absorption with a strong plasmonic peak around ∼425 nm due to the localized surface plasmon resonance (LSPR) of Ag NPs of average size ∼6.0 nm. Spectroscopic analysis of the Ag-BP hybrid ascertains strong light-matter interactions around the LSPR band of Ag NPs. The size-dependent optical response of BP nanostructure/Si state-of-the-art broadband (300-1600 nm) photodiodes has been studied extensively. The enhancement of broadband photoresponse characteristics is demonstrated using the plasmonic Ag-BP 0D-2D hybrid nanostructure compared to pristine BP, where the peak responsivity in the former is shifted to the visible region (∼440 nm) compared to UV response (∼340 nm) of the latter. The tunable spectral responsivity with a peak value of ∼3.2 A/W (@ ∼440 nm and -5 V) for the Ag-BP/Si heterojunction device demonstrates the potential of plasmonic BP hybrids for future nanophotonic devices.