Negative space charge

Figure 36. Stored negative space charge (a), coupled electric field (b), and internal voltage (c) in anodic oxide during anodization (curve 1) and during isothermal aging at various times (curves 2-7).61...

Figure 38. Calculated j-U curves for dielectric with negative space charge (solid curves) and reference uncharged one (dashed curve). The insets illustrate curve linearization in log j- U and log j-Ul/2 coordinates.62...

Let us note one vital point, which is of methodological importance. It has been traditionally accepted in electrochemistry to choose the positive direction of the electrode potential

positive electrode charge. Here the zero potential is assumed to be that of the reference electrode, which coincides, within a constant, with the potential in the solution bulk (— oo). On the other hand, in physics of semiconductor surface the potential is usually reckoned from the value in the semiconductor bulk ( ) the enrichment of the surface with electrons, i.e., the formation of a negative space charge, corresponding to the positive potential of the surface. In particular, this statement directly follows from the Boltzmann distribution for electrons and holes in the space-charge region in a semiconductor ... 

Structures or compounds which are ion exchangers have an intrinsic-structural charge, <7, which can be expected to shift the ZPC away from the calculated value by a variable amount. Prolonged exposure to extreme pH may result in adsorption or desorption of protons resulting in a positive or negative space charge, hence a finite basic direction. Negative <7i should move the ZPC in the acid direction. 

Fatuzzo and Coppo (146) observed that the negative space charge at the surface of their large crystals of silver bromide was reversed when the surface was covered by silver sulfide. 

Verwey-Niessen model — Earliest theoretical model of the - interface between two immiscible electrolyte solutions (ITIES) assuming the existence of a diffuse double layer with one phase containing an excess of the positive space charge and the other phase an equal excess of the negative space charge [i] (Figure). The difference of - inner electric potentials, Afcj> = (f>w - [Pg.692]

In the so-called thermionic diode, a heated collector electrode is simply brought into the vicinity of the laser beam and isolated towards the vessel walls. No extraction voltage is applied and the ion current flowing as a result of the decreasing negative space charge around the collector, as a result of the ionization by the laser,... 

It should be mentioned that for p-type materials, usually, a negative space charge is formed because the work function of the semiconductor is below that of the metal. Again assuming an ideal contact, the energy barrier is given by... 

The thermionic current grows with electric field until the negative space charge near the cathode is eliminated and saturation is achieved. This saturation, however, is rather relative. A further increase of electric field leads gradually to an increase of the saturation current level, which is related to a reduction of work function due to an electric field known as the Schottky effect ... 

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