Growth mechanism and characterization of rose-like microspheres and hexagonal microdisks of ZnO grown by surfactant-free solution method

Highly crystalline rose-like microspheres made of nanosheets and hexagonal microdisks of zinc oxide (ZnO) were grown on Si and ZnO/Si substrates, respectively in solution at 90 °C without the use of any surfactants. The microdisks had lower defects and better optical properties than the microspheres and showed a strong UV emission at 378 nm. A possible growth mechanism based on the electrostatic forces between polarized ZnO nanostructures and substrates and the surface energy was proposed for the growth of microspheres and microdisks.