Photoluminescence from ZnO nanoparticles in vapor phase

Photoluminescence (PL) is observed from ZnO nanoclusters formed in ZnO plasma due to cooling of plasma species by passing a collimated beam of fourth harmonic (266 nm) of Nd:YAG (yttrium aluminum garnet) laser through ZnO plasma formed by third harmonic (355 nm) of Nd:YAG laser. A shift of 42 meV in peak position of PL profile of ZnO clusters from that observed in bulk ZnO is seen, which shows the effect of quantum confinement. The behaviors of PL profiles are studied at varying ablating intensities with fixed probe intensity. A superlinear increase in PL peak intensity with narrowing of emission linewidth above a particular ablating intensity is observed. The defect related emission band, usually occurring due to oxygen vacancy, is not observed from the ZnO clusters formed due to cooling of laser induced ZnO plasma. The observed redshift of PL peak positions with increasing ablating intensities could be due to temperature-induced band gap shrinkage arising due to enhancement of electron temperature. (C) 2008 American Institute Of Physics. [DOI: 10.1063/1.2977756]