Chemical etching activation

Another application involves the measurement of copper via the radioisotope Cu (12.6-hour half-life). Since Cu decays by electron capture to Ni ( Cu Ni), a necessary consequence is the emission of X rays from Ni at 7.5 keV. By using X-ray spectrometry following irradiation, sensitive Cu analysis can be accomplished. Because of the short range of the low-energy X rays, near-surface analytical data are obtained without chemical etching. A combination of neutron activation with X-ray spectrometry also can be applied to other elements, such as Zn and Ge. 

In the ion induced damage mechanism energetic ions break crystal bonds on the film surface thereby making the film more accessible and more reactive to the active chemical etchant. However, the side walls remain relatively unperturbed, and etching proceeds at the nominal chemical etch rate. Consequently, material removal proceeds far more rapidly in the ion flux direction, resulting in anisotropy. In actuality, the surfaces exposed to the plasma are likely to be composed of a chemisorbed coating of etchant... 

Transparent, conducting, tin oxide coatings are used in applications where light must pass through the substrate in order to strike the active element such as a photoconductive or photoelectric material. Chemically deposited films of silicon dioxide serve as masks on semiconductor materials for selective doping in the preparation of integrated circuits that can later be removed by chemical etching. 

The same molecule has been used as probe to evaluate the SERS efficiency of substrates where ligand molecules are located in a sandwich configuration between two metal surfaces both SERS active [10]. The first one belongs to a silver plate, whose surface roughening was produced via chemical etching with ammonia and hydrogen peroxide the second is a layer of silver colloidal particles deposited after chemisorption of the ligand molecules, as shown in Fig. 20.16. 

Some nonconductors, for example polymers like polycarbonates and polystyrenes, must be subjected to a surface treatment prior to activation in order to get good adhesion of palladium nuclei. Surface treatment can include the use of chemical etchings for plastics or reactive gas plasma treatments [56]. 

The third route is defined as substractive (lUPAC), in that certain elements of an original structure are selectively removed to create pores. Examples include the formation of porous metal oxides by thermal decomposition of hydroxides, of porous glasses by chemical etching, of activated carbons by controlled pyrolysis, of ceramic foam membranes by burning off a polymer (e.g. polyurethane), of alumina by anodic oxidation of aluminium to give oriented cylindrical pores with a narrow size distribution. 

So far only thermal effects and chemical etching have been investigated systematically, mostly for glass machined with an active cathode. The following discussion will therefore concentrate on glass micromachining. 

As more OH radicals are present in the case of an active anode than for an active cathode, chemical etching is also more important. Consequently, the surfaces are smoother than those obtained by cathodic machining [63,120]. However, when using anodic polarisation, the tool-electrode will be anodically dissolved resulting in high tool wear. 

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