3-DIMENSIONAL TRANSMISSION ELECTRON-MICROSCOPY OBSERVATIONS OF SUPPORTED PALLADIUM PARTICLES

Transmission electron microscopy (TEM) is an extensively used technique for the characterization of small supported particles. In addition to the usual projectional TEM data such as the size distribution, number density, and crystallographic structure of the aggregates, the three-dimensional shape of these clusters can also be determined when ''microsupports'' are used. This work presents the first TEM and high-resolution transmission microscopy (HRTEM) results of supported palladium clusters grown by UHV vapor deposition on alumina microspheres in the surface profile imaging mode. For this metal/support system, the viability of TEM analysis with and without stabilizing ''fixing layers'' is assessed. Furthermore, in order to extend this technique to other metal/support systems, we will examine whether a sublayer between the particle and the microsupport can be used to easily change the nature of the support surface. The results of this study also emphasize important limitations of the present profile-TEM technique, especially when applied to cluster deposits of chemically active metals.