Microsc. Microanal. Microstruct. 4, 297-304 (1993)
DOI: 10.1051/mmm:0199300402-3029700

High-resolution electron microscopy of fine particles

M. Mitome¹, Y. Ohshima², M. Itoh³ et K. Takayanagi<sup>3

1</sup>  CANON Research Center, Morinosato-Wakamiya, Atsugi-Shi, Kanagawa, 243-01, Japan
²  Fujitsu Laboratories Ltd. 10-1 Morinosato-Wakamiya, Atsugi, 243-01, Japan
³  Tokyo Institute of Technology, Materials Science and Engineering, 4259 Nagatsuda, Midori-ku, Yokohama, 227, Japan

Abstract
Structures of fine particles which contains 30 - 104 atoms have been investigated by UHV high-resolution electron microscopy. Three topics on structural anomaly of fine particles are described and discussed: structural instability, surface anomaly, and a new intermediate phase related with surface melting. Anomalous surface reconstruction is generated on a (111) facet of Ge particle, which has not been found on the bulk surface of the same orientation, as well as fine particles of Au have specific n x 1 (n = 3, 5, 7) surface reconstructions on (100) facet. In the case of Sn particle, no apparent surface reconstructions have been recognized, while some irregularity of the surface layer have been noticed for particles less than the critical size (2r = 5 nm), which indicates surface disordering or melting. Below the critical size appears an intermediate phase between liquid and solid phase, where crystal embrios seem to be generated and annihilated within the particle. To determine structures and dynamic changes of fine particles with such irregularity, a new imaging method of high-resolution electron microscopy has been proposed: A convergent beam illumination (CBI), instead of parallel beam illumination (PBI), produces atom image at the right position even specimens of an irregular structure.

PACS
6114L - Convergent-beam electron diffraction, selected-area electron diffraction, nanodiffraction.
6837 - Microscopy of surfaces, interfaces, and thin films.

Key words
High-voltage electron microscopy -- High-resolution methods -- In situ -- Convergent beam method -- Surface structure -- Surface reconstruction -- Phase transformations -- Structural instability -- Nanoparticles


© EDP Sciences 1993