Surface space charge height

A more realistic model will take full account of the atomic nature of the surface and yield charge densities and electronic potentials similar to those obtained by the jellium model. In this circumstance, however, the charge density on the solid side of the surface exhibits fluctuations that are often called Friedel oscillations and which are due to the screening by the free electrons (Figure 5.1). The amplitude of this oscillation is a sensitive function of the electron density, as are the height and extent of the surface space-charge potential. 

Gas adsorption on insulator or semiconductor surfaces can cause very large changes in the height of the surface space-charge potential and its Debye length. As... 

The schemes in Figs. 44 and 45 may serve to summarize the main results on photoinduced microwave conductivity in a semiconductor electrode (an n-type material is used as an example). Before a limiting photocurrent at positive potentials is reached, minority carriers tend to accumulate in the space charge layer [Fig. 44(a)], producing a PMC peak [Fig. 45(a)], the shape and height of which are controlled by interfacial rate constants. Near the flatband potential, where surface recombination... 

There are various driving forces that result in the formation of space charge across surfaces or interfaces. Perhaps the simplest example is the case of a Schottky diode that is formed from a metal-semiconductor heterojunction. For an ideal metal-semiconductor contact, the height of the potential barrier is given by... 

The much lower concentration of mobile charge carriers in a semiconductor causes a much more extended distribution of electric excess charge underneath the surface (diffuse space charge layer). Therefore, the variation of electric field strength in the surface which changes height... 

What are the consequences of the existence of a space charge layer for electrode reaction kinetics First of all, the electrical field strength in the surface is small and is very little changed by a variation in the potential applied. The height of the energy barrier for ion transfer is therefore little affected. 

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