Direct lattice imaging of small metal particles

Observations on small vapour-deposited particles of silver and gold with direct lattice imaging in the Cambridge University 600 kV high-resolution electron microscope have established unambiguously the presence of dislocations in particles as small as 15nm in diameter. The detailed structure of more complicated ' polyparticles ' can also be characterized directly. Knowledge of the internal and surface structure of small metallic particles is basic to an understanding of the nucleation of thin metal films and any explanation of their important role in heterogeneous cataIysis. Observations using electron diffraction and electron microscopy have proved invaluable in elucidating their crystallography, in particular in establishing the existence of multiple twinning within many particles (In0 1966, Ino and Ogawa 1967, Allpress and Sanders 1967). These so-called multiple-twinned particles (MTPs) are known to be composed of either five or twenty tetrahedra which make up decahedra or icosahedra. (The icosahedral MTPs have a simila