Correlations among size, defects, and photoluminescence in ZnO nanoparticles

Abstract:

We studied the correlations among size, defects, and photoluminescence emissions in ZnO nanoparticles of sizes ranging from 25 to 73 nm. The impurities and defects were characterized by Fourier-transform infrared spectroscopy and Raman spectroscopy. Particles of larger size revealed fewer surface impurities and enhanced E2 mode of hexagonal ZnO crystals, while the oxygen vacancy centers did not vary significantly with particle size. A simultaneous increase of excitonic luminescence and defect luminescence intensities with the increase of particle size is shown, indicating both emissions are subjected to nonradiative quenching by near surface defects. The study on the size-dependent green luminescence in our samples suggests that the emission might be a bulk property instead of having a surface origin in nanostructured ZnO. Two different radiative recombination processes are involved in the excitonic emission of ZnO. While the slow decay component (370 ps) did not depend on particle size, the fast component varied from 56 to 96 ps. We attribute the slow component to free exciton recombination, while the fast component is attributed to near surface exciton recombination. © 2007 American Institute of Physics.

Año de publicación:

2007

Keywords:

Fuente:

scopus