EXTENDED ELECTRON ENERGY-LOSS FINE-STRUCTURE AND SELECTED-AREA ELECTRON-DIFFRACTION STUDIES OF SMALL PALLADIUM CLUSTERS

Extended electron energy-loss fine structure (EXELFS) and selected-area electron diffraction (SAED) techniques have both been applied to the study of the crystalline structure of Pd clusters of average diameters ranging from bulk to 24 angstrom. The combined use of these techniques gives complementary information about the crystalline structure of Pd clusters. Both techniques show the same lattice parameter expansion, about 4% for the smallest Pd cluster, with respect to the bulk. The EXELFS analysis performed on the Pd-M4,5 edge shows a sizeable increase of structural disorder in the smallest cluster. SAED gives additional information about the Pd bulk sample, showing the occurrence of crystalline regions about 50 angstrom in diameter.