Pinning of the Fermi level

Equation (7.32) underlines the pinning of the Fermi levels of metal electrodes with the solid electrolyte and reminds the fact that the absolute electrode potential is a property of the solid electrolyte and of the gaseous composition but not of the electrode material.21... 

By comparing Figure 11.9 and the characteristic Po2(Uwr) rate breaks of the inset of Fig. 11.9 one can assign to each support an equivalent potential Uwr value (Fig. 11.10). These values are plotted in Figure 11.11 vs the actual work function G>° measured via the Kelvin probe technique for the supports at po2-l atm and T=400°C. The measuring principle utilizing a Kelvin probe and the pinning of the Fermi levels of the support and of metal electrodes in contact with it has been discussed already in Chapter 7 in conjunction with the absolute potential scale of solid state electrochemistry.37... 

Degeneracy can be introduced not only by heavy doping, but also by high density of surface states in a semiconductor electrode (pinning of the Fermi level by surface states) or by polarizing a semiconductor electrode to extreme potentials, when the bands are bent into the Fermi level region. 

Dietl et al. 2001c). There exists another mechanism by which strain may affect 7c. It is presently well known that the upper limit of the achievable carrier concentration is controlled by pinning of the Fermi level by impurity or defect states in virtually all compound semiconductors. Since the energies of such states in respect to bands vary strongly with the bond length, the hole concentration and thus 7c will depend on strain. 

The Fermi level pinning is related to the defect structure of the material and therefore to the preparation of the CdS films.9 The particular defects, which lead to the pinning of the Fermi level in CdS, are, however, not yet identified. 

D. Troost et al.. Pinning of the Fermi level Close to the Valence-Band Top by Chlorine Adsorbed on Cleaved GaAs (110) Surfeces, J. Vac. Sci. Technol. 1987, B5(4), 1119-1124. 

Fig. 15.5 Models of the electronic DoS in amorphous materials leading to a pinning of the Fermi level at midgap. a Cohen-Fritzshe-Ovshinsky model with overlapping band tails, b dangling bond model, and c negative U defect model with charged defects (adapted from [25])...

Guo, G., Liu, L., Chu, K., Jayanthi, C., 8c Wu, S. (2005). Electromechanical responses of single-walled carbon nanotubes Interplay between the strain-induced energy-gap opening and the pinning of the Fermi level. Journal of Applied Physics Letters, 98, 044311. 

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