Investigations on LSPR effect of Cu/Al nanostructures on ZnO nanorods towards photodetector applications

In this paper, we have investigated the room temperature photoluminescence spectra of Cu/Al nanoparticles coated ZnO nanorods for optoelectronic applications. Pulsed laser deposition technique was used to cote the metal nanoparticles on ZnO nanorods. We have done a detailed investigation on photoluminescence spectra of Cu/Al coated ZnO nanorods where we have observed significant enhancement of near band edge emission and remarkable suppression of deep level emission. Such enhancement of near band edge emission and suppression of deep level emission might be due to the arise of several physical consequences, such as exciton–plasmon coupling, hot carrier formation, defect passivation and enhanced electric field at metal (Cu/Al)-semiconductor (ZnO) junction. We have observed ~7.6 times and ~2 times near band edge emission enhancements in Cu and Al coated ZnO nanorods, respectively. Further, a planar type photodetector device was fabricated by using pure Cu as a planar electrode on top of the metal coated ZnO nanorods. We have studied the value of currents in Cu/Al coated ZnO nanorods compared to the pristine ZnO nanorods at dark and UV illumination conditions. We have observed that the current value of Cu coated ZnO nanorods increases nearly 4 orders higher in magnitude in comparison to the pristine ZnO nanorods under UV illumination. However, the value of current in Al coated ZnO nanorods increases little less i.e. ~3 orders higher in magnitude in comparison to the pristine ZnO under UV illumination condition. Hence, Cu/Al coated ZnO nanorods could be a potential candidate for the UV light sensing. Furthermore, we can claim that Cu/Al coated ZnO nanorods is a promising alternative towards the development of earth abundant metal based stable and efficient nano-plasmonic devices.