SYNCHROTRON RADIATION CHARACTERIZATION OF COBALT NANOPARTICLES FORMED BY ION IMPLANTATION

Abstract

Ion implantation of Co into silica layers and subsequent thermal annealing were used to form Co nanoparticles. Structural characterization was performed using X-ray Absorption Spectroscopy and Small Angle X-ray Scattering to determine, respectively, the local atomic structure and size distribution of the Co nanoparticles as a function of annealing temperature. For decreasing nanoparticle size, a bond-length contraction, an increase in Debye–Waller factor and a reduction in coordination number were observed. The bond-length contraction was related to the capillary pressure in the nanoparticles while an increase in Debye–Waller factor reflected an increase in disorder attributed to the high surface-area-to-volume ratio of small nanoparticles. X-ray Absorption Near Edge Structure spectroscopy revealed that the annealing conditions had a significant effect on the nanoparticle crystal structure and oxidised Co fraction.