Fabrication of semiconductor microspheres with laser ablation in superfluid helium

We fabricated semiconductor ZnO microspheres via the pulsed laser ablation in the superfluid helium. The scanning electron microscope observation revealed the high sphericity and smooth surface. We also observed whispering gallery mode resonances, the electromagnetic eigenmode resonances within the microspheres, in the cathodoluminescence spectrum, verifying the high symmetry of the fabricated microspheres. Further, we cross-sectioned the microspheres with using focused ion beam. The scanning electron microscope observation of the cross section uncovers the existence of small holes within the microspheres. The inner structure examination helps us to understand the microscopic mechanism of our fabrication method.