Electron sensitization

In SEM and STEM, all detectors record the electron current signal of tire selected interacting electrons (elastic scattering, secondary electrons) in real time. Such detectors can be designed as simple metal-plate detectors, such as the elastic dark-field detector in STEM, or as electron-sensitive PMT. For a rigorous discussion of SEM detectors see [3],... 

Scanning Auger Electron Spectroscopy (SAM) and SIMS (in microprobe or microscope modes). SAM is the most widespread technique, but generally is considered to be of lesser sensitivity than SIMS, at least for spatial resolutions (defined by primary beam diameter d) of approximately 0.1 im. However, with a field emission electron source, SAM can achieve sensitivities tanging from 0.3% at. to 3% at. for Pranging from 1000 A to 300 A, respectively, which is competitive with the best ion microprobes. Even with competitive sensitivity, though, SAM can be very problematic for insulators and electron-sensitive materials. 

Fig. 2.1. Plausible mechanisms of influence of metal particles deposited on adsorbent on adsorption-caused response of its electrophysical characteristics a - chemical sensitization the dope particles cause the activation and spill-over of adsorbate b - electronic sensitization the dope particles become donors or acceptors of electrons in dependence on the conditions in gas phase.

Substituents without strong donor or acceptor character (e.g., phenyl, succinimido) give mixtures. The reason for the increased electronic sensitivity is thought to be the... 

A color television set contains an array of electron-sensitive phosphors. Three different phosphors are used, one emits red light, another emits green light, and the remaining one... 

For the photoreceptor made of high-resistivity film containing oxygen, no treatment is required for the blocking property either at its free surface or at the contact to the electrode, implying that the electronic sensitivity is lost either at its surface or in the bulk. 

The first step was to spin-coat an electron-sensitive polymer (polymethylmethacrylate (PMMA)) onto an oxidized Si(l 00) wafer (which serves as a Si02 support). The desired pattern is subsequently written into the polymer layer by a highly collimated electron beam, followed by the selective dissolution of the polymer damaged by the electron exposure. A thin film of platinum is then deposited on this mask, and after the remaining polymer resist is removed completely by dissolution, metal particles remain on the substrate and are located at the positions of the prior electron irradiation, typically forming an ordered array of nanoparticles. 

Electron-beam Electron-sensitive Good control of Slow, residual Smaller hne width. 

Spin-coating of one or two layers of an electron sensitive polymer film or resist (step 2). 

Two catalyst mechanisms, chemical and electronic, proposed by Yamazoe and coworkers [37, 38], are shown in figure 14.4 [38]. In chemical sensitization, gas would first adsorb to the metal ( M in the figure), then spill over to the Sn02 semiconductor. Perhaps more likely, the electronic sensitization effect is noted by the direct exchange of electrons between the metal and the semiconductor. The oxidation state of the metal is changed upon contact with the gas electron exchange increases and subsequently changes the conductivity of the semiconductor. 

F-T. Lentes, Electron-Sensitive Coatings (Review Paper), in Thin Films on Glass,... 

Varlot, K., J.M. Martin, D. Gonbeau and C. Quet. 1999. Chemical bonding analysis of electron-sensitive polymers by EELS. Polymer AO 5691-5697. 

PE spectroscopy has also been a significant factor in the development of quantum chemistry. lEs provide electronically sensitive benchmarks against which different computational methods may be tested. Conversely, quantum chemistry, especially density functional theory (DET), has been invaluable in the assignment of PE spectra. 

Guidi concludes that an electronic sensitization exists for the platinum. Furthermore, the results indicate the existence of an optimal size for the metallic particles, which gives the maximum sensitivity to the tested films... 

Finally, let us mention that electronic interaction through metal-metal bonds at the surface of small particles has been postulated to account for selectivity modifications obtained by introduction of selective poisons or ligands, in heterogeneous metallic catalysts [118]. The effect is the highest with the smallest particles which would exhibit the highest electronic sensitivity similar conclusions have been reached from theoretical calculations [119]. 

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