Synthesis of Spherical ZnO Microcrystals by Laser Ablation in Air

We have succeeded in synthesizing the zinc oxide (ZnO) microspheres by laser ablation of a ZnO sintered target in air, and have demonstrated ultraviolet whispering-gallery-mode lasting from the sphere under ultraviolet pulsed laser excitation. In this study, we investigated the dependence of the laser fluence and the spot size on the growth of the ZnO microspheres. Large sizes of more than 30 μm microspheres were synthesized with increasing the laser fluence up to 440 J/cm². Although undesired nanoparticles and fragments were also generated at high fluence and large ablation spot size, selective collection of the microspheres can be expected because of different emitting distributions of the microspheres and other fragments.