Effects of Pt capping and annealing on the photoluminescence properties of ZnO nanorods

Pt-capped ZnO nanorods were synthesized by the thermal evaporation of a mixture of ZnO and graphite powder at 900 °C followed by Pt sputter-deposition and thermal annealing. Photoluminescence (PL) showed that the intensity of near-band edge (NBE) emission of ZnO nanorods was enhanced significantly by Pt-capping and annealing in a H2 atmosphere. The intensity ratio of NBE emission to the deep level emission, INBE/IDL of the Pt-capped ZnO nanorods after annealing in a H2 atmosphere was ∼11 times higher than that of the unannealed, uncapped ZnO nanorods. The increase of the INBE/IDL might be due to a combination of carrier transfer from the defect level to the Fermi level of Pt nanoparticles, surface plasmon resonance in Pt nanoparticles and hydrogen passivating deep level defects.