Plasma electroreflectance

As an important example, let us consider the effect of electroreflection due to inhomogeneity of the distribution of free carriers in the space-charge region of a semiconductor (plasma electroreflection). The contribution of the electrons to the complex dielectric permittivity (an n-type semiconductor is considered for illustration and the contribution of the holes is neglected) is given by the expression (see, for example, Ziman, 1972)... 

Let us note that according to Eq. (73) the sign of plasma electroreflection is determined by the sign of sc. The quantity A R/R is positive if 0 (accumulation layer) and is negative if , < 0. In other words, the flat band potential of the semiconductor can be determined from the condition that the sign of A R/R changes. 

Figure 8. Comparison of true charge transfer coefficients q for chloride (a) and bromide (b) estimated from plasma electroreflectance data (smooth poly crystalline Pt) with X and Y values in solutions of the same anionic composition (c - chloride, d - bromide, dispersed electro-deposited platinum). The area between two curves (a, b) corresponds to unavoidable scatter (boundaries present to limiting versions of q recalculation). Dashed fragments (a) correspond to the region of lower accuracy, as compared to the overall potential region. Reprinted from Refs. 195 (a, b) and 194 (c, d). Copyright (1990) and (1969), respectively, with permission of Nauka Publ.

Another important point of data analysis is to find a relation between the dielectric properties of the electrode-electrolyte interface and its microscopic characteristics. A rigorous treatment of this problem is rather complex and involves large-scale computer calculations. An alternative method is to use semi-phenomenological models which relate the behavior of the dielectric tensor components to different features of the electron spectrum of the system. The mechanisms responsible for modulated electroreflectance can be classified as those arising from the modulation of the electron density in the selvedge region of the electrode (plasma electroreflectance), and from those which are due to a modulation of both interband and intraband optical transi-... 

---