Electron charge concentration density

Assume is -25 mV for a certain silica surface in contact with O.OOlAf aqueous NaCl at 25°C. Calculate, assuming simple Gouy-Chapman theory (a) at 200 A from the surface, (b) the concentrations of Na and of Cr ions 10 A from the surface, and (c) the surface charge density in electronic charges per unit area. 

Figure 7.3 Truncated representation of p versus the distance from the nucleus for a spherically symmetric electron density of a free sulfur atom (3P). (b) Truncated representation of L(r) at the same scale as (a). This function reveals the three shells K, L, and M constituting the sulfur atom. Each shell consists of a region of local charge concentration (dark areas) and a region of local charge depletion (light...

Let us consider a solid that contains only one type of electron trap of volume density N at the discrete level ( and a set of occupied deeper electron traps of density M. The experiment is performed in a temperature range in which traps N empty but traps M remain thermally disconnected and act only as an untapped reservoir of trapped electrons. The density of recombination centers is unspecified, but a density/of them is empty. AtT = Tq, a concentration of /o empty recombination centers exists due to excitation. At these conditions, charge neutrality of the sample is of the form... 

In metals, the concentration of mobile electrons is enormously high so that the excess charge is confined to a region very close to the surface, within atomic distances [14, 15]. In semiconductors with substantially less charge carrier density, on the other hand, a region of spatial charge distribution can be found [16, 17]. 

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