Novel micrometer-sized ZnO balls have been synthesized on (111)-Si substrates via pyrolysis of zinc acetate in oxygen atmosphere. The ZnO microballs exhibit unique geometrical shapes with partly porous or hollow structures and their walls are composed of large size textured ZnO microcrystals. The growth mechanism of the ZnO microballs is proposed to be a process following the formation of ZnO film layer, ZnO branches and then ZnO microballs. The phase structure and crystalline structure of the as-grown ZnO microballs were investigated by X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM), respectively. The room-temperature photoluminescence (PL) spectrum shows prominent UV emission around 394 nm and weak green emission peaks indicating that there are few defects in the single crystal grains of the ZnO microballs. (c) 2005 Elsevier B.V. All rights reserved.