Influence of Ni, Ti and NiTi alloy nanoparticles on hydrothermally grown ZnO nanowires for photoluminescence enhancement

Abstract

In this work, surface-plasmon mediated enhanced photoluminescence emission has been investigated on Ni, Ti, and NiTi coated ZnO nanowires (NWs). ZnO NWs have been synthesized using a facile hydrothermal process, where NWs are coated with three different metals (Ni, Ti, and NiTi) using sputter deposition technique. It has been found that there is a significant improvement in near band edge emission (NBE) and passivation in deep level emission (DLE) in such metal embedded ZnO NWs and these emission properties can be tuned as we change the metal. Notably, we have achieved the highest enhancement of ∼6 times in NBE and best suppression of ∼15 times) in DLE by alloying of such metals (Ni and Ti). Such a remarkable DLE suppression is attributed to the presence of defect centers in ZnO NWs. The defect transition energy of ZnO is in resonance with the surface plasmon energy of metal nanoparticles, which leads to the conversion of DLE into NBE. The enhancement of NBE and suppression of DLE are possible due to the surface plasmon resonance coupling between metal nanoparticles (NPs) and ZnO NWs. Therefore, we conclude that earth abundant metals, such as Ni and Ti show significant SPR coupling on ZnO NWs and the alloying (NiTi) of such metals presents further improved SPR compared to the respective individual metals.