Hot holes behind the improvement in ultraviolet photoresponse of Au coated ZnO nanorods

• Au coated ZnO nanorods have been utilized for UV photodetection.
• Decay of plasmons into hot carriers play significant role in photodetection.
• Hot holes will migrate to the ZnO VB level, thus will enhance the photocurrent.
• Transition from excitonic to bimolecular recombination has been observed.

Surface plasmon resonance mediated by Au was utilized to enhance the UV response of ZnO nanorods (NRs) based photodetectors. The value of the exponent of radiative recombination mechanism has shown an increment from 1.54 to 1.86 indicating transition from excitonic recombination to electron-hole bimolecular recombination with Au coating. Kubelka-Munk absorption spectra for Au coated samples have shown both transverse and longitudinal plasmon resonance at 450 nm and 700 nm, respectively indicating presence of interband transitions. The decay of surface plasmons into hot carriers (hot holes here) can be assigned for improved photosensitivity (defined here as the ratio of photocurrent to the dark current, measured at −3 V applied bias) of photodetector from 87.8 to 950.4, with the covering of Au.

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