Investigations on laser ablated NiTi and CuAl alloyed nanoparticles and their influence on the LSPR effect at the interface of ZnO nanostructures

Abstract

In this work, surface-plasmon mediated enhanced photoluminescence emission has been investigated on NiTi and CuAl coated ZnO nanorods (NRs). ZnO NRs have been synthesized using a facile hydrothermal process. The photoluminescence (PL) spectra of ZnO nanostructures generally show two distinctive emissions, which are near band edge emission (NBE) in the UV region and deep level emission (DLE) in the visible region irrespective of the growth technique. Such DLE usually arises from the high density of defects present in ZnO nanostructures leads to the trapping of charge carriers. This result in significant carrier loss and hindering of luminescence intensity. Therefore, any reduction in DLE should efficiently enhance the NBE of ZnO nanostructures. Recent investigations have shown that the metal nanoparticles (NPs) play a major role in PL emission enhancement of ZnO nanostructures where ZnO nanostructures are coated with metal nanoparticles (NPs). Therefore, coating with earth abundant metal-based alloys (NiTi, and CuAl) on ZnO is a good alternative towards achieving significant PL emissionenhancement. We have explored four different coating techniques (direct laser dispersion, spin coating, pulsed laser deposition and sputter deposition) of alloy NPs on ZnO to study the changes in its PL emission spectra. It has been found that there is a significant improvement in NBE and passivation in DLE of such metal embedded ZnO NRs. The PL emission can be tuned as we change the metal and the coating techniques. Notably, we have achieved the highest enhancement of ~ 20 times in NiTi coated ZnO and ~8 times in CuAl coated ZnO NRs through sputter deposition technique. The enhancement of NBE and suppression of DLE attributed to the surface plasmon resonance coupling between metal nanoparticles (NPs) and ZnO NRs. Therefore, we conclude that earth abundant metal-based alloys (NiTi and CuAl) can show significant SPR coupling on ZnO NRs compared to the respective individual metals.