Electron microscopy investigation of structure and morphology of small supported metal particles of palladium

The morphology and crystallographic structure of small palladium particles prepared by condensation onto NaCl(001) and mica substrates were investigated using electron diffraction and high resolution defocused dark field and strong beam and weak beam dark field transmission electron microscopy imaging techniques. Sample tilting through large angles was used to characterize particles with a rhombic outline and with irregular outlines. Thus, under conditions with very low deposition rates, it is possible to obtain decahedral or icosahedral particles of which a very high proportion have f.c.c. structure. These results are the opposite of previous ones. On NaCl(001) substrates, the proportion of decahedral particles is about 90% and the size can reach 2000 A. On mica substrates, the proportion of icosahedral particles 150 A in size is about 95%.