Impurity concentration manifestation

E qierimental investigations of these semiconductors confirm that the impurily atoms do interact with one another. This interaction is manifested above all in the process of formation of free carriers at high impurity concentrations. In Fig. la we have plotted esqierimental results obtained in a study of n-type Ge and Si [1]. Along the ordinate we have plotted the density of free electrons n in the conduction band of the semiconductor, i.e., the density deduced from measurements of the Hall coefficient the total (chemical) concentration N of impurity atoms introduced into the crystals is plotted along the abscissa. This concentration was determined by radioactive analysis. 

The arbitrary division of behaviour has been made because of the extreme behaviour of some chemicals that initiate small areas of attack on a well-passivated metal surface. The form of attack may manifest itself as stress-corrosion cracking, crevice attack or pitting. At certain temperatures and pressures, minute quantities of certain chemicals can result in this form of attack. Chloride ions, in particular, are responsible for many of the failures observed, and it can be present as an impurity in a large number of raw materials. This has led to the development of metals and alloys that can withstand pitting and crevice corrosion, but on the whole these are comparatively expensive. It has become important, therefore, to be able to predict the conditions where more conventional materials may be used. The effect of an increase in concentration on pitting corrosion follows a similar relationship to the Freundlich equation where... 

Another type of structure may result from localized resonance states formed by either traps or impurities in the film39 (see Fig. 6B). In this case, the electrons are localized at the trap and due to the high charge concentration strong electron-vibration interactions exist that result in inelastic processes in the film. While these traps are observed clearly in LEET,39 in the LEPS experiments they are manifest by reduction in the transmission probability and sometimes by charging effects, but cannot be observed as modulation on the amplitude of the spectra. 

Under certain stringent conditions, all ion reactivity is concentrated on propagation. The resulting polymerizations are living. In other cases, the instability of the ions is manifested by a complex of poorly defined reactions leading to transfers, retardation, and decay of the polymerizing activity of the centres, i.e. termination. Termination is either an inherent feature of the respective polymerizing system or it may be caused by accidental impurities or, finally, it may be a consequence of deliberately added compounds. 

Possible mechanisms of an impurity effect on the photoluminescence properties of the Si02 nc-Si are summarized. The experimental data manifested the action of these mechanisms are presented. It is shown that, depending on the kind of the impurity, its concentration and annealing conditions, the enhancement or quenching of the photoluminescence associated with Si nanocrystals can be observed. 

As manifested in the growth of potassium sulfate (Figure 4), here also chromium(lll) is very effective in suppressing the growth rate of ammonium sulfate crystal. The unsteady state impurity action is evident at various chromium(III) concentrations. 

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