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Open Access Nano Express

Effect of surrounding environment on atomic structure and equilibrium shape of growing nanocrystals: gold in/on SiO2

F Ruffino12*, C Bongiorno2, F Giannazzo2, F Roccaforte2, V Raineri2 and MG Grimaldi1

Author Affiliations

1 MATIS CNR-INFM and Dipartimento di Fisica e Astronomia, Università di Catania, via S. Sofia 64, 95123, Catania, Italy

2 Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e Microsistemi (CNR-IMM), Stradale Primosole 50, 95121, Catania, Italy

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Nanoscale Research Letters 2007, 2:240-247  doi:10.1007/s11671-007-9058-4

Published: 8 May 2007

Abstract

We report on the equilibrium shape and atomic structure of thermally-processed Au nanocrystals (NCs) as determined by high resolution transmission electron microscopy (TEM). The NCs were either deposited on SiO2surface or embedded in SiO2layer. Quantitative data on the NCs surface free energy were obtained via the inverse Wulff construction. Nanocrystals inside the SiO2layer are defect-free and maintain a symmetrical equilibrium shape during the growth. Nanocrystals on SiO2surface exhibit asymmetrical equilibrium shape that is characterized by the introduction of twins and more complex atomic defects above a critical size. The observed differences in the equilibrium shape and atomic structure evolution of growing NCs in and on SiO2is explained in terms of evolution in isotropic/anisotropic environment making the surface free energy function angular and/or radial symmetric/asymmetric affecting the rotational/translational invariance of the surface stress tensor.

Keywords:
Nanocrystal; Crystal growth; Transmission electron microscopy; Wulff plot; Surface energy; Gold; SiO2