Dopant ions choice

Lewis acid-induced polymerization is also a relatively convenient means to obtain conducting polymers. As with anodic electropolymerizations, monomers are oxidized by an external source, but in this instance electron transfer occurs from the monomer or growing chain to the chemical oxidant. Of the various Lewis acids that are readily available, FeCl3 has become the most popular choice given its effectiveness and low cost. Scheme 7 shows a typical polymerization where the resulting polymer is obtained in its conducting state with FeCl4" dopant ions. 

In an explanation of the reasons for choice of such dopant ions, Angelopoulos et al. [79] noted that to obtain a radiation induced insolubility in P(ANi) suitable for certain resist applications, the emeraldine base form must be doped with materials which produce protonic acids when irradiated, primarily "onium" salts such as triphenylsulfonium hexafluoroantimonate. Thus in a typical application, NMP solutions of emeraldine base and this onium salt are mixed and spin coated on a substrate. When exposed to 240 nm UV radiation at ca. 100 - 300 mJ/cm, the initial blue film turns green, characteristic of conductive P(ANi). This conductive P(ANi) is insoluble in NMP, whereas the non-irradiated, blue, non-conductive film is... 

Diffusion. Another technique for modifying the electrical properties of siUcon and siUcon-based films involves introducing small amounts of elements having differing electrical compositions, dopants, into substrate layers. Diffusion is commonly used. There are three ways dopants can be diffused into a substrate film (/) the surface can be exposed to a chemical vapor of the dopant at high temperatures, or (2) a doped-oxide, or (J) an ion-implanted layer can be used. Ion implantation is increasingly becoming the method of choice as the miniaturization of ICs advances. However, diffusion is used in... 

In addition to nanostructural properties of the conducting polymer, considerable influence on actuation behavior has been demonstrated due to the choice of electrolyte. This has included properties of the solvent employed, and crucially the size of doping ions and their interaction with the conducting polymer. As mentioned above, PPy films doped with moderately small anions (e.g. CP) lead to actuation driven by anion movement. By contrast, it is generally found that the inclusion of a large dopant anion (e.g. DBS) within PPy leads to cation-driven actuation, typically when a smaller cation is employed (e.g. Na ). However, it is not always a simple matter of predicting which movement, anion or cation, will predominate for a particular electrolyte system, and for a particular type of... 

Dynamic SIMS using chemically active atomic or small molecular primary ion beams (Cs" ", 0 , O2 ) provides the utmost in detection limits in localized elemental analysis. As a result, this is the technique of choice for following dopant distributions as a function of depth in the semiconductor industry (a sector of Materials Sciences) and for mapping isotopic dishibutions in the Earth Sciences (for further details, see Section 1.2.3). Little in the way of molecular information is accessible under these conditions. 

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