Boosted photoresponsivity using silver nanoparticle decorated TiO2 nanowire/reduced graphene oxide thin-film heterostructure

Here, we report on the fabrication and use of a silver (Ag) nanoparticle (NP) decorated TiO2 nanowire (NW)/reduced graphene oxide (RGO) thin-film (TF) heterostructure as a UV detector, using a controlled method called the glancing angle deposition technique. Transmission electron microscope images show Ag NPs (size 7-13 nm) covering the entire surface of the TiO2 NWs. A high absorption as well as photoluminescence for the Ag NP-TiO2 NW/RGO TF sample reveals the generation of a large number of electron-hole pairs compared to bare TiO2 NW. The resulting plasmonic UV photodetector from the Ag NP-TiO2 NW/RGO TF exhibits a rectification ratio of 5039 (+10 V) and responsivity of 1760 A W−1 at 350 nm light (with power density as low as 0.58 µW cm−2). Moreover, the device shows fast response speed (rise time of 157 ms and fall time of 488 ms) with detectivity and noise equivalent power of 6.659 × 1013 Jones and 51 fW, respectively. The enhanced plasmonic field and high scattering of light, along with the high mobility RGO layer at the bottom, result in the superior performance of the device.