Time-resolved photoluminescence study of the stimulated emission in ZnO nanoneedles

Abstract

ZnO nanoneedles were fabricated by thermal evaporation of Zn nanoparticles at 800 °C and atmospheric pressure. The samples showed strong ultraviolet photoluminescence and weak orange defect luminescence. Time-resolved photoluminescence (TRPL) was measured using the Kerr-gated fluorescence technique in order to probe the ultrafast carrier dynamics in exciton-exciton scattering and electron hole plasma (EHP) regimes. In both regimes, the decay time of the photoluminescence is very fast (∼1 ps). Even though no structure is detected in the time-integrated spectra of the EHP emission, the TRPL reveals the coexistence of the excitons and free carriers. Possible reasons for the observed phenomena are discussed. © 2005 American Institute of Physics.published_or_final_versio