Penetration depth of electrons

The surface sensitivity of most electron probe techniques is due to the fact that the penetration depth of electrons into metals falls to a minimum of 4 to 20 A when their kinetic energy is between 10 and 500 eV. It is also convenient that electrons at these energies have de Broglie wavelengths on the order of angstroms. With a monochromatic beam, it is possible to do LEED. 

The penetration depth of electrons into the substrate decreases at lower energy. Also, the surface dose per mA of beam current increases (see Figure 3.26) and thin coatings and inks can be cured with higher efficiency... 

The electronic structures of porous solids have been examined by X-ray photoelectron spectroscopy (XPS). However, the penetration depth of electrons is 1 nm at best and XPS cannot examine electronic structures of inner pore-walls. XPS has been often used for the determination of surface chemical structures such as surface functional groups in activated carbon. Ar etching leads to the depth profile of electronic structures. This depth profile is often effective to evidence the presence of nanoporosity. 

Spectroscopic methods have recently been developed that are able to probe the surface species at the water/air interface. The use for this purpose of photoelectron spectroscopy depends on the short penetration depths of electrons and the electron binding energy specificity. Bohm et al. (1994) applied photoelectron spectroscopy... 

The phenomena of beam broadening as a function of specimen thickness are illustrated in Fig. 4.20 each figure represents 200 electron trajectories in silicon calculated by Monte Carlo simulations [4.91, 4.95-4.97] for 100-keV primary energy, where an infinitesimally small electron probe is assumed to enter the surface. In massive Si the electrons suffer a large number of elastic and inelastic interactions during their paths through the material, until they are finally completely stopped. The resulting penetration depth of the electrons is approximately 50 pm and in the... 

The elemental composition, oxidation state, and coordination environment of species on surfaces can be determined by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) techniques. Both techniques have a penetration depth of 5-20 atomic layers. Especially XPS is commonly used in characterization of electrocatalysts. One common example is the identification and quantification of surface functional groups such as nitrogen species found on carbon-based catalysts.26-29 Secondary Ion Mass spectrometry (SIMS) and Ion Scattering Spectroscopy are alternatives which are more surface sensitive. They can provide information about the surface composition as well as the chemical bonding information from molecular clusters and have been used in characterization of cathode electrodes.30,31 They can also be used for depth profiling purposes. The quantification of the information, however, is rather difficult.32... 

The selection of EB equipment depends on the foam thickness and production rate. The foam manufacturers throughout the world are using equipment with electron accelerators with voltages ranging from 0.5 to 4 MV and power ratings from 10 to 50 kW. The penetration depth of a 1 MV unit is approximately 3 mm (0.12 in.). Irradiation on both sides doubles the thickness capability. ... 

Electron Microprobe. Since the electron beam diameter is only 1 /xm, it is unlikely that the volume sampled represents the bulk composition. To obtain as representative analyses as possible, the focal spot is electronically scanned over a square area of 300 /xm X 300 /xm. In some cases, where one dimension of the section was < 300 /xm, the area scanned was necessarily reduced to 100 /xm X 100 /xm. Assuming a penetration depth of 1 /xm (5), the standard 300 /xm square raster samples a volume of <— 9 X 104 /xm3 = 1 /xgram. 

The interaction of X-rays with matter is weak compared to that of electrons. This leads to a large penetration depth of some /xm... 

Polymeric fullerene materials can be obtained by many methods, for example by irradiation with electrons or ions, treatment in a plasma generator, doping with alkali metals [9,28,46], direct chemical synthesis [47], or mechanical milling [29]. Because of the small penetration depth of light fullerenes can only be photopolymerized as thin films, but bulk photopolymer can be obtained by polymerization in solution [48,49]. Diffraction studies show that photopolymers usually have a disordered fee structure. Although some ordered films have been... 

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