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 x 10(17) and 2 x 10(17) ions/cm(2), respectively. In the as-implanted sample, Zn nanoparticles with average crystalline size of similar to 4.5 nm were observed to have formed and were distributed from the sample surface to a depth of similar to 76 nm. The implanted sample was thermally annealed at a temperature of 700 degrees C in a mixture of Ar and H-2 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 similar to 17.5nm were formed. Due to the O- ion implantation, a thickness of similar to 38nm of Si wafer was transformed into SiO2, and the SiO2 layer thickened to similar to 57nm 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. (C) 2012 The Japan Society of Applied Physics