Flat band potential surface dipoles

The main effect of crystal orientation is caused by different barrier heights on different crystal faces. It is well known that Volta-potential differences are dependent on crystal orientation because the surface dipole differs for different faces. In the case of a semiconductor electrode this means that the flat band potential which can be determined experimentally depends... 

Here, Ws is the work function of electrons in the semiconductor, q is the elementary charge (1.6 X 1CT19 C), Qt and Qss are charges located in the oxide and the surface and interface states, respectively, Ere is the potential of the reference electrode, and Xso is the surface-dipole potential of the solution. Because in expression (2) for the flat-band voltage of the EIS system all terms can be considered as constant except for tp (which is analyte concentration dependent), the response of the EIS structure with respect to the electrolyte composition depends on its flat-band voltage shift, which can be accurately determined from the C-V curves. 

Besides the effects of different surface dipoles, the concentration and energy position of surface states depend also largely on surface orientation with the result that the electric excess charge in surface states can be very different on different surfaces. This is indicated in Figure 3 by a comparison between the flat band situation and the situation at equal electrode potential for different surfaces. Case (a) is a surface free of surface... 

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