This paper surveys experimental results concerned with secondary electron emission of surfaces bombarded by primary electrons with respect to scanning electron microscopy. The energy distribution, the angular distribution, and the yield of secondary electrons from metals and insulators are reviewed as well as the escape depth of the secondary electrons and the contribution of the backscattered electrons to the secondary electron yield. The different detectors for secondary electrons in the scanning electron microscope are described. The contrast mechanisms in the scanning electron microscope, material, topography, voltage, magnetic, and crystallographic orientation contrast based on secondary electron emission, as well as the lateral resolution, depending among other things on the spatial distribution of the emitted secondary electrons, are discussed.
Practical methods are investigated to reduce the charging which is often observed during AES analysis of insulating samples with keV electrons. It is shown that the negative charge caused by electron beams with keV energy can be either avoided or considerably reduced by the me of an additional electron beam or by the supply of lowenergy (500 eV) positive ions. It is also reported and discussed that the state of reduced or vanishing charging obtained by both methods can be maintained for long periods of time.
Electron energy loss spectroscopy (EELS) in a transmission electron microscope (TEM) and photoacoustic spectroscopy (PAS) has been used to study the electronic structure of small Ag, In and Au particles, deposited on thin carbon foils, quartz supports or as self-supporting layers, respectively.In the low energy-loss region the EELS spectra of Ag particles with diameters of ca. 50 nm are different from the spectra of the homogeneous Ag layers, mainly owing to the influence of the carbon foil. By decreasing the packing density of the Ag particles, a shift of the plasma losses to lower energies is observed in the energy region 10eV. The optical behaviour of homogeneous metallic and small particle layers on thin quartz supports was studied by PAS in the ultraviolet/visible (UV/VIS) spectral region. The homogeneous layers, e.g. of Ag, show, in the UV range, the well known change of reflectance due to an interband transition of bare silver. For Ag particle layers surface plasma resonances are excited. With increasing packing density of the particles the absorption peak observed is red-shifted and becomes broader, whereas the results of EELS in the low energy-loss region revealed a shift to higher energies.To obtain additional information investigations of In and Au particles were performed.
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