Electron beam effects

Surface Tool Concerns. Because surface chemistry was of prime interest in the McIntyre study, XPS was chosen as the technique to use. Often AES can provide chemical information, but previous XPS work had shown easily identifiable oxidation states of U2O5 and l Og suggesting that XPS was a good choice and avoiding possible electron beam effects that AES might induce. 

Bermudez VM. (1999) Low-energy electron beam effects on poly(methyl methacrylate) resist films. / Vac Sci Technol S 17 2512-2518. 

Summarizing, photoinduced and ion or electron beam effects include oxidation, hydrogen release, dangling bond creation, and creation of reactive molecular species. Ion bombardment can in addition introduce a variety of point defects in the silicon skeleton. Highly focused beams, such as used in micro-Raman, can cause thermally induced hydrogen exodiffusion, sintering, defect creation, etc. An awareness of potential irradiation effects is important in both the characterization and processing of porous silicon. 

As it is shown above, the processing of the alloying surface by the electron beam with energy density of the electron beam 20 J/cm and above is accompanied by extensive melting of the surface layer of steel. After 5... 15 pulses of the electron beam effect the islands and the nodules of copper, presenting on the surface of the steel, subjected to EEA are not detected by methods of scaiming microscopy. The surface of the samples is fully smoothed. After 25 and 50 pulses of the electron beam effect on the surface one can see a large number of craters. 

It is found that the structure of the dendrites depends on the number of pulses of the electron beam effect. When the number of pulses being, changed within the limits of 5... 15, on the surface of the steel the dendritic structure with the axes of the first order is formed (so-called structure of cellular crystallization). With a larger number of pulses of the electron beam (25 and 50 pis.) the dendrites mainly have the arises of the first and the second order. 

Electron beam effects in AES the heating effect of the electron beam causes evaporation, diffusion and segregation, and thus an incorrect estimate of the composition, particularly for thin films on glass substrates [77]. The effect can be reduced if the electron beam current density is lowered. 

E 983-10 Guide for minimizing unwanted electron beam effects in Auger electron... 

Once the primary electron beam is created, it must be demagnified with condenser lenses and then focused onto the sample with objective lenses. These electron lenses are electromagnetic in nature and use electric and magnetic fields to steer the electrons. Such lenses are subject to severe spherical and chromatic aberrations. Therefore, a point primary beam source is blurred into a primary beam disk to an extent dependent on the energy and energy spread of the primary electrons. In addition, these lenses are also subject to astigmatism. AH three of these effects ultimately limit the primary beam spot size and hence, the lateral resolution achievable with sem. 

Instmmentation for tern is somewhat similar to that for sem however, because of the need to keep the sample surface as clean as possible throughout the analysis to avoid imaging surface contamination as opposed to the sample surface itself, ultrahigh vacuum conditions (ca 10 -10 Pa) are needed in the sample area of the microscope. Electron sources in tern are similar to those used in sem, although primary electron beam energies needed for effective tern are higher, typically on the order of ca 100 keV. 

Electron-beam melting of zirconium has been used to remove the more volatile impurities such as iron, but the relatively high volatiUty of zirconium precludes effective purification. Electrorefining is fused-salt baths (77,78) and purification by d-c electrotransport (79) have been demonstrated but are not in commercial use. 

Donor and acceptor levels are the active centers in most phosphors, as in zinc sulfide [1314-98-3] ZnS, containing an activator such as Cu and various co-activators. Phosphors are coated onto the inside of fluorescent lamps to convert the intense ultraviolet and blue from the mercury emissions into lower energy light to provide a color balance closer to daylight as in Figure 11. Phosphors can also be stimulated directly by electricity as in the Destriau effect in electroluminescent panels and by an electron beam as in the cathodoluminescence used in television and cathode ray display tubes and in (usually blue) vacuum-fluorescence alphanumeric displays. 

Nonradiative surface recombination is a loss mechanism of great importance for some materials (e.g., GaAs). This effect, however, can be minimized by increasing the electron-beam energy in order to produce a greater electron penetration range. 

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