Fabrication of P-, Sb-, and Mg-doped ZnO spherical microcrystals by laser ablation in air

We have succeeded in growing the ZnO spherical microcrystals by a simple laser ablation in air, and we have obtained ultraviolet (UV) whispering-gallery-mode (WGM) lasing from the sphere under pulsed laser excitation. In this growth technique, a solid ZnO target is rapidly heated by laser-induced plasma, and melted target is splashed from the irradiated spot as droplets. Then, the droplets are crystallized into spherical shapes by the surface tension during the dropping process. This rapid melting and solidifying process may be effective for doping impurities into ZnO. In this study, we fabricated P-, Sb-, and Mg-doped ZnO microspheres, and investigated their structures and optical properties. A blue-shift of UV WGM lasing from Mg-doped ZnO microsphere was obtained, indicating that the band-gap engineering of ZnO microsphere grown by the simple ablation technique was achieved.