Electronic enhancement

C2.18.3.5 MODEL STUDIES OF PHOTON- AND ELECTRON-ENHANCED ETCHING... 

Gillis H P, Choutov D A, Steiner P A IV, Piper J D, Crouch J H, Dove P M and Martin K P 1995 Low energy electron enhanced etching of Si(IOO) in hydrogen-helium DC plasma App/. Phys. Lett. 66 2475-7... 

Gillis H P, Choutov D A, Martin K P, Pearton S J and Abernathy C R 1996 Low energy electron enhanced etching of GaN/Si in hydrogen DC plasma J. Electrochem. Soc. 143 L251-4... 

Theatrical Pyrotechnics or Special Effects. Many spectacular visual and audible effects are produced for stage presentations of both music and drama, and many motion pictures and television shows incorporate pyrotechnic and explosive special effects to Hven up the presentation. These spectacular effects are a combination of pyrotechnics, explosives, combustion, and electronics. After the effects are filmed or videotaped, they are often enhanced by slow-motion replay and by the addition of more exciting noise. A real explosion is over in milliseconds, and hence there is a need for electronic enhancement to create a more spectacular effect on the screen. 

Loudiana, M.A., Dickinson, J.T., Schmid, A. and Ashley, E.J. (1987) Electron enhanced sorption of fluorine by silver surfaces. Applied Surface Science, 28, 311-322. 

T. van Woudenbergh, J. Wildeman, P.W.M. Blom, J.J.A.M. Bastiaansen, and B.M.W. Langeveld-Voss, Electron-enhanced hole injection in blue polyfluorene-based polymer light-emitting diodes, Adv. Fund. Mater., 14 677-683, 2004. 

In a reversed-phase liquid chromatography system, if the hydrogen-bonding and Coulombic forces are negligible, the retention of molecules depends upon their size, and the presence of n electrons enhances the selectivity. The molecular size, i.e. the van der Waals volume, can be calculated by hand, by Bondi s method,29 or by certain computer programs. 

The key fxmctions of the CRO industry include improving cycle time, increasing quality and lowering the cost of therapeutic product development. A critical element of that process is the adophon of computer-based electronic enhancements (IT applied to the product development segment of the research and development continuum). Compared... 

Although the majority of authors who have investigated CNTs as supports for Pt and PtRu particles claim higher activity or performance compared to conventional catalysts, it is not clear why these enhancement arise. It seems unlikely that the CNTs provide any electronic enhancement to Pt(Ru) reactivity, so it is likely that CNTs provide benefits for catalyst layer structure. Part of this may be related to surface area because CNTs can have relatively high surface areas and are often compared to XC72 supported catalysts that have only a moderate surface area ( 250 m g ). Given the current high expense of these materials ( 10 kgr ), further benefits of their use need to be identified before fhey can be practically considered as candidates for fuel cell catalyst supports. 

It is this authors opinion, that ion and electron enhanced chemical reactions of the type described above are probably important in MOST situations. Nevertheless, to our knowledge, neither a theoretical understanding nor well defined experiments have been reported on this subject. Therefore, several experiments which have been performed recently in this laboratory will be described and then possible explanations for the ion-enhanced, chemical reactions will be discussed. 

Many of the mechanisms discussed in Sect. 2.2.6.1 with regard to ions may also apply to chemical reactions enhanced by electron bombardment. A discussion of that type will not be repeated in this section. However, a mechanism for the electron-enhanced etching of SiOj can be suggested on the basis of processes which are known to occur. It is known, for example, that electron bombardment of SiOj causes oxygen to be desorbed into the gas phase, i.e., electron stimulated desorption occurs . The silicon which remains upon the surface can now be attacked by the XeFjfgas) to produce SiF4(gas). In this manner both oxygen and silicon are removed from the SiOj lattice and the material is etched. The chemistry involved is likely to be more complex, but this simple model illustrates a possible mechanism. 

In summary, delocalization of electrons enhances stability, and we can visualize delocalized bonding by using the resonance method. In later chapters we will leam more about the effects of resonance on chemical equilibrium and on the kinetics of chemical reactions of organic compounds. 

Although the methyl groups in acetylacetonate complexes retard some reactions by steric hindrance, they provide some electronic enhancement in reactions with electrophiles and furthermore protect the donor oxygen atoms from electrophilic attack. These properties have been discerned by a comparison of the numerous reactions of acetylacetone complexes with the relatively few successful reactions of complexes of formylacetone and malondialdehyde. 

Auger emission to neutralize incoming ions leaves the solid surface in an excited state relaxation of the surface results in secondary electron generation (23, 24). Secondary electrons are ejected when high-energy ions, electrons, or neutral species strike the solid surface. These electrons enhance the electron density in the plasma and can alter the plasma chemistry near a solid surface. Radiation impingement on a surface can induce a number of phenomena that depend upon the bombardment flux and energy. 

Fraser, R. R. Mansour, T. S. Aridity measurements with lithiated amines steric reduction and electronic enhancement of acidity. /. Org. Chem. 1984, 49, 3442-3443. 

Low energy electron-enhanced etching (LE4) uses a DC plasma in which electrons with energies <15 eV and reactive species at thermal velocities are incident on a sample. The sample is also heated at temperatures ranging from 50 to 250°C. Gillis et al [26,27] used hydrogen and chlorine plasmas to produce highly anisotropic etch profiles and smooth etch surfaces, at etch rates of 50 - 70 nm/min. 

Figure 19-8. Low energy electron enhancement factor (LEEEF) as a function of photon energy for SSB and DSB production in a monolayer of DNA deposited on tantalum...

Most generally, spur aspects appear whenever a chemically very active compound (essentially, electron scavengers) is present in the solid matrix, either as a normal constituent or as an additive. This has been demonstrated recently in a variety of irradiated polymers, where radiolysis of the matrix induces the production of either free radicals, inhibiting Ps formation by electron scavenging, or of trapped electrons, enhancing the Ps formation probability, depending on the temperature [41]. 

Sn and alkali metals (Li, Na and K) can reduce coke covering on the Pt active site of a propane dehydrogenation catalyst, Pt/y-Al203. The role of the alkali metals is to increase excess mobile electrons of the catalyst surface. Sn and Sn-alkali metal promoted catalysts show higher excess mobile electrons than unpromoted ones. The excess mobile electrons enhance hydrogen spillover on the catalyst surface, thus reducing the amount of coke deposits. 

The Encyclopedia is available in a printed text and an online version. The online version includes everything in the print version while also providing the convenience of a keyword search engine. New articles and revised articles will be digitally posted quarterly and available to all subscribers of the electronic version as soon as available. Although the content will initially parallel the print version, unique electronic enhancements will be available on the online version. 

Fig. 4 shows that the source radiation intensity can be reduced from 1000 microwatts [/cm ] to 10 microwatts [/cm ], without a tremendous loss in the oscillatory resistance signal. Indeed, even 1 microwatt [/cm ] yields observable oscillations withont supplementary electronic enhancement. We expect that the application of balanced bridge and/or modulation techniques ate likely to provide sensitivity to even lower power levels, into the nanowatt [/cm ] level. 

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