Auger characteristic

Figure 14 shows the auger characteristic throughput over pressure gradient for an extruder with auger diameter 500 mm and a ceramic brick... 

The slope of the auger characteristic is very small, hence the high stiffness (viscosity > 2 bar s). Therefore the shear stress and the dissipation function yield much higher values (please mention the different axis distribution for the two compounds). 

XPS shares the Auger characteristics of good surface sensitivity since this is driven by the same need for the electrons to be able to reach the detector unscathed. It is possible to vary the depth of analysis in both techniques by varying the tilt angle with regard to the detector. This technique is used more extensively in XPS where it is often called angle resolved depth profiling. 

In aes, the resolution is largely independent of the characteristics of the analy2er or source and is dictated by the natural linewidth of the Auger line (usually several eV). Therefore, in using a CMA for aes, the analyst is more concerned with transmission (and hence, sensitivity) than with resolution. In contrast to xps, the optimhation of variables is achieved for aes in the CRR mode of operation. The large transmission of the CMA relative to the CHA make it the more desirable analy2er for aes. 

AES = auger electron spectroscopy APS = appearance potential spectroscopy CEELS = characteristic electron energy-loss spectroscopy ... 

Once an inner shell vacancy is created in an atom the atom may then remrn toward its ground state via emission of a characteristic X ray or through a radiationless Auger transition. The probability of X-ray emission is called the fluorescence yield. 

The inelastic collision process is characterized by an inelastic mean free path, which is the distance traveled after which only 1/e of the Auger electrons maintain their initial energy. This is very important because only the electrons that escape the sample with their characteristic Auger energy are usefrd in identifying the atoms in... 

If an incident electron beam of sufficient energy for AES is rastered over a surface in a manner similar to that in a scanning electron microscope (SEM), and if the analyzer is set to accept electrons of Auger energies characteristic of a particular element, then an elemental map or image is again obtained, similar to XPS for the Quantum 2000 (Sect. 2.1.2.5). 

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. 

The availability of high-intensity, tunable X-rays produced by synchrotron radiation has resulted in the development of new techniques to study both bulk and surface materials properties. XAS methods have been applied both in situ and ex situ to determine electronic and structural characteristics of electrodes and electrode materials [58, 59], XAS combined with electron-yield techniques can be used to distinguish between surface and bulk properties, In the latter procedure X-rays are used to produce high energy Auger electrons [60] which, because of their limited escape depth ( 150-200 A), can provide information regarding near surface composition. 

Figure 7. Dependence of the kinetic energy of the Ag M4VV Auger-transition on BE of the Ag 3ds/2 core level during ion bombardment of the Ag islands. The characteristic energies of certain silver compounds and alloys are also shown for comparison. (Data compiled from Ref [163].)...

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