The influence of annealing conditions on the growth and structure of embedded Pt nanocrystals

The growth and structure of Pt nanocrystals NCs formed by ion implantation in a-SiO2 has been investigated as a function of the annealing conditions. Transmission electron microscopy and small-angle x-ray scattering measurements demonstrate that the annealing ambient has a significant influence on NC size. Samples annealed in either Ar, O2, or forming gas 95% N2: 5% H2 at temperatures ranging from 500 °C–1300 °C form spherical NCs with mean diameters ranging from 1–14 nm. For a given temperature, annealing in Ar yields the smallest NCs. O2 and forming gas ambients produce NCs of comparable size though the latter induces H chemisorption at 1100 °C and above, as verified with x-ray absorption spectroscopy. This H intake is accompanied by a bond-length expansion and increased structural disorder in NCs of diameter 3 nm. © 2009 American Institute of Physics. DOI: 10.1063/1.3079506