Doping permanent

In molecular doped polymers the variance of the disorder potential that follows from a plot of In p versus T 2 is typically 0.1 eV, comprising contributions from the interaction of a charge carrier with induced as well as with permanent dipoles [64-66]. In molecules that suffer a major structural relaxation after removal or addition of an electron, the polaron contribution to the activation energy has to be taken into account in addition to the (temperature-dependent) disorder effect. In the weak-field limit it gives rise to an extra Boltzmann factor in the expression for p(T). More generally, Marcus-type rates may have to be invoked for the elementary jump process [67]. 

In order to provide resolution in two-dimensions, the light sensitive material is subdivided into an array of pixels, as shown in Fig. 5. These pixels are defined by electric fields that are created within the light sensitive material. The electric fields can be generated one of two ways (1) permanently defined by implanting (doping) a very small amount of another material, or (2) programmably defined by electric fields produced by wires in the solid state electronics. 

Samarium salts are used in optical glass, capacitors, thermoionic generating devices, and in sensitizers of phosphors. The metal is doped with calcium fluoride crystals for use in lasers. It also is used along with other rare earths for carbon-arc lighting. Its alloys are used in permanent magnets. 

Alkali-Metal-Free Solutions. Films of CD PbS are usually p-type as deposited. One early suggestion to explain this was that the alkali metal ions used in the deposition solution (as NaOH or KOH) act as a p-type dopant [33]. Based on this supposition, Bloem deposited PbS from a solution of PbAci, hydrazine hydrate, and thiourea (free of Na or K). The as-deposited films were initially n-type but changed to p-type on exposure to air. Attempts to dope the films permanently n-type by adding trivalent ions to the deposition solution were unsuccessful. However, by depositing the films on a substrate coated with trivalent ions (such as Al, In, Ga), n-type behavior could be maintained for a considerable time. PbS p-n junctions were fabricated using this approach (see Chap. 9). 

Permanently doped polymers, concerned with chemical or protonic doping. The charges that appear on the polymer chains are compen-... 

Finally, still in the area of permanently doped polymers, we mention gas separation, which has a very large potential market in the domain of chemical separation. Preliminary work has shown that membranes very promising for gas separation can be made with CPs [111], typically polyaniline or polypyrrole [112]. The basic points are as follows (1) thin CP... 

Stabilizers are physically lost from the polymer by evaporation and leaching and their concentration in the polymer drops. As a consequence, polymer articles are no more chemically protected. Physical factors limiting the lifetime of stabilizer doped polymers due to the physical impermanence of stabilizers are explained in Sect. 1.3.1. Factors influencing the efficacy of the two permanent and impermanent stabilizers due to the physical interaction with the polymer matrix are given in Sect. 1.3.2. 

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