Characterization of Small Metallic Clusters by Electron Energy Loss Spectroscopy

Small spherical tin and gallium clusters (diameters in the range 2 to 80 nm), prepared with a liquid metal ion source, were analysed in a scanning transmission electron microscope (STEM) by electron energy loss spectroscopy (EELS). Both volume and surface plasmon excitations were investigated and their dependence on the cluster size interpreted by classical and quantum mechanical models. A blue shift of the volume plasmon energy with decreasing radius R of the cluster was clearly detected. The full width at half maximum (FWHM) of the peak, related to the damping of the volume plasmon excitation, showed a dependence in 1/R. The reported variation of the surface plasmon energy with R was consistent with earlier predictions or experiments

EELS ANALYSIS OF A PRECIPITATE IN V3Si BY STEM AND HVEM

Nous avons effectué l'analyse d'un précipité dans V3Si (structure A15) par spectroscopie de pertes d'énergie en microscopie électronique classique à haute tension (1000 kV) et à balayage (100 kV), par transmission. Compte tenu du diagramme de phases du système binaire V-Si, l'analyse a permis de penser qu'il s'agissait de V5Si3. Ce résultat a été confirmé par microdiffraction électronique en faisceau convergent.The analysis of a precipitate in V3Si (A15 structure) has been performed by transmission EELS with a HVEM (1000 kV) and with a STEM (100 kV). Taking into account the phase diagram of the V-Si system, the composition V5Si3 is anticipated. This result has been confirmed by convergent beam electron microdiffraction