Electron Energy-Loss Spectroscopy Studies of Supported Small Metal Particles and Surfaces.

Electron energy-loss spectroscopy (EELS) has been used for studying the surface plasmon excitations in supported metal particles. Systematic theoretical and experimental investigations have been carried out on a postulated half -embedded particle model in specimen of Al/{ rm AlF}_3 and Al/Al. A base on which to develop a better understanding of the support -particle interaction (SPI) has been established. The important effects of the supports on the metal particle's electronic properties have been confirmed by comparing the excitation behavior of the supported metal particle with that of the isolated metal particles. The effects of SPI on the metal particle's catalytic properties have been studied in the Co/{rm La_2O}_3 and Co/{rm CeO}_2 intermetallic catalysts. A technique, REELS, in which EELS has been used in conjunction with reflection electron microscopy (REM) for studying the chemical compositions, atomic coordinations and electronic properties in surface layers of crystals has been developed. A relative 15 +/- 5eV shift on the M edge energy thresholds of Au (111) and Pt (111) surfaces has been observed, and is considered to be a property of the surfaces. The modification of density of states and the excitation of surface states have been observed on the MgO (100). The quantitative analysis of the MgO (100) indicates that there is oxygen absorption on the surface. The distinct excitations of the Ga-L and As-L edges on the GaAs (110) under various surface resonance conditions have been attributed to surface channelling effects. Good agreement is found with the dynamical calculations of the electron channelling behavior along different atomic columns. The dynamical scattering processes of electrons and the processes of creation of the reflection wave in the RHEED geometry have been investigated. The surface "monolayer" resonance effect has been observed on GaAs (100) surface, and can be used for identifying the atomic termination on the surface. It is shown that quantitative analysis of the surface chemical composition is feasible in REELS.