Electron Appearance Potential Fine

EAPFS Electron Appearance Potential Fine-Structure A fine-structure technique (see EX-AFS). Core-holes are excited by monoenergetic electrons at 1 KeV. The modulation in the excitation cross section may be monitored through adsorption, fluorescence, or Auger emission. 

EAPFS Extended (Electron) Appearance Potential Fine Structure Analysis ... 

EAPFS Electron appearance potential fine structure... 

Figure 12. Extended appearance potential fine structure observed from the Ga-Auger peak in GaAs (001) surface as a function of inddent electron ener E. The figure is reproduced by permission from ref. [89].

Auger electron appearance potential spectroscopy Auger electron spectroscopy Atomic force microscopy Azimuthal photoelectron diffraction Appearance potential spectroscopy Angle-resolved Auger electron spectroscopy Angle-resolved photoemission extended fine structure... 

Appearance potential methods all depend on detecting the threshold of ionization of a shallow core level and the fine structure near the threshold they differ only in the way in which detection is performed. In all of these methods the primary electron energy is ramped upward from near zero to whatever is appropriate for the sample material, while the primary current to the sample is kept constant. As the incident energy is increased, it passes through successive thresholds for ionization of core levels of atoms in the surface. An ionized core level, as discussed earlier, can recombine by emission either of a characteristic X-ray photon or of an Auger electron. 

In this section, the application of APS to the study of surface phenomena will be discussed. The section is divided into three parts. In the first part, the elucidation of electronic structure of the surfaces of semiconductors and metals by APS is described with suitable examples. The second part deals with the phenomenon of adsorption of gases on metallic surfaces leading to the formation of compounds. The third and final part examines the determination of local structure of semiconductor surfaces from the fine structure observed on the high energy side of an appearance potential edge. 

Another difficulty is that all these subsystems have to function at once, i.e., the development, characterization, and optimization of the individual subsystems is limited, and there is no way of a mechanical fine tuning. This means that the total system has to be designed on very reliable simulations and pattern transfer, which comprise not only the geometrical features for potentials and trajectories of electrons and ions, but also the behavior of the mass separator or pressure regimes in different areas of the system. Such an approach may appear rather adventurous and risky at least it may and will take much more time to generate a working system than the demonstration of a single subsystem implemented into a standard mass spectrometer environment. 

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