Bond length contraction in Au nanocrystals formed by ion implantation into thin SiO2

Au nanocrystals (NCs) fabricated by ion implantation into thin SiO2 and annealing were investigated by means of extended x-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy. A bond length contraction was observed and can be explained by surface tension effects in a simple liquid-drop model. Such results are consistent with previous reports on nonembedded NCs implying a negligible influence of the SiO2 matrix. Cumulant analysis of the EXAFS data suggests surface reconstruction or relaxation involving a further shortened bond length. A deviation from the octahedral closed shell structure is apparent for NCs of size 25 Å. © 2004 American Institute of Physics. [DOI: 10.1063/1.1803619]