Sensitization process, spectral

The detection of spectral sensitizing action often depends on amplification methods such as photographic or electrophotographic development or, alternatively, on chemical or biochemical detection of reaction products. Separation of the photosensitization reaction from the detection step or the chemical reaction allows selection of the most effective spectral sensitizers. Prime considerations for spectral sensitizing dyes include the range of wavelengths needed for sensitization and the absolute efficiency of the spectrally sensitized process. Because both sensitization wavelength and efficiency are important, optimum sensitizers vary considerably in their stmctures and properties. 

Nuclear magnetic resonance traditionally has had low sensitivity and spectral resolution. It can provide rigorous quantification of analytes, but not accurate qualitative identification. Individual resonances may be sensitive to the chemical and physical environment of the molecule, which then requires appropriate preparation of samples. The process also has little dynamic range, in contrast to GC-MS. 

In this chapter, the motivations to adopt MLR systems for optical e-beam, x-ray, and ion-beam lithographic systems will be given, followed by a survey of published MLR systems. Specific practical considerations such as planarization, pinhole and additive defects, interfacial layer, etch residue, film stress, interference effects, spectral transmission, inspection and resist stripping will be discussed. The MLR systems will be compared in terms of resolution, aspect ratio, sensitivity, process complexity and cost. 

The effectiveness of the spectral sensitization depends on many factors. As a rule, a spectral sensitization process needs the thermal activation energy of the... 

The shallow and deep levels play the important role in the sensitization process. Detailed research in this field has shown the presence of four local electron centers in the energetic spectrum of the sensitized PVC in the range 0.6-3.3 eV [63,64]. The density of localized states was of the order 1018 1019 cm-3. These can play essential role in spectral and chemical sensitization due to their influence on photogeneration, recombination and charge transfer processes. 

Finally, dyes may be used in several imaging processes to extend the inherent spectral sensitivity of an imaging process to longer wavelengths, especially to visible or near infrared regions of the spectrum. These sensitization processes are industrially very important to provide panchromatic sensitivity or sensitivity to special light sources such as lasers. This review will describe those spectral sensitization processes which involve electron transfer, but will ignore those processes based on more conventional mechanisms. 

Furthermore, exchange transfer is also less sensitive to changes in spin multiplicity than resonance transfer. Therefore, it is the mechanism responsible for the triplet-to-singlet energy transfer in the spectral sensitization processes of organic photochemistry, as seen in organic resist materials. 

With reduced sensor cost the range of appHcations now includes thermal vision (2,3) industrial processing, industrial security, poHce work (3), maritime safety, airline safety and vision enhancement for night driving and flying and weather sateUites. For these appHcations, the thermal sensor typically uses a broad spectral band to achieve highest sensitivity. 

Chemical Gas Detection. Spectral identification of gases in industrial processing and atmospheric contamination is becoming an important tool for process control and monitoring of air quaUty. The present optical method uses the ftir (Fourier transform infrared) interference spectrometer having high resolution (<1 cm ) capabiUty and excellent sensitivity (few ppb) with the use of cooled MCT (mercury—cadmium—teUuride) (2) detectors. 

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