Formation of ZnO Nanoparticles by ZnO- and O- Dual Beam Ion Implantation and Thermal Annealing

ZnO nanoparticles have been synthesized by dual beam ion implantation into Si. 45 keV ZnO- molecular ions and 15 keV O- ions were implanted into Si at room temperature to fluences of 1 ×1017 and 2 ×1017 ions/cm2, respectively. In the as-implanted sample, Zn nanoparticles with average crystalline size of ~4.5 nm were observed to have formed and were distributed from the sample surface to a depth of ~76 nm. The implanted sample was thermally annealed at a temperature of 700 °C in a mixture of Ar and H2 for 1 h, after which both the Zn and O spatial distributions were observed to have broadened and ZnO nanoparticles with average crystalline size of ~17.5 nm were formed. Due to the O- ion implantation, a thickness of ~38 nm of Si wafer was transformed into SiO2, and the SiO2 layer thickened to ~57 nm when the sample was annealed. Binding energies of Zn increased in the annealed sample as compared to the as-implanted sample for all measured depths, consistent with the formation of ZnO bonding and indicating that ZnO had formed throughout the SiO2 layer and slightly beyond.