Conductance effects, with space-charge

In the r.h.s. part of the figure the excess conductance is normalized with respect to the space charge width (2A ifL > 4A and L if L < 4A) being a measure of the mean conductivity of the space charge zone. This value remains constant in the regime of trivial size effects but increases according to g(L) in the regime of true size effects. 

Because of the different potential distributions for different sets of conditions the apparent value of Tafel slope, about 60 mV, may have contributions from the various processes. The exact value may vary due to several factors which have different effects on the current-potential relationship 1) relative potential drops in the space charge layer and the Helmholtz layer 2) increase in surface area during the course of anodization due to formation of PS 3) change of the dissolution valence with potential 4) electron injection into the conduction band and 5) potential drops in the bulk semiconductor and electrolyte. 

Semiconductor - Electrolyte Interlace The electric field in the space charge region that may develop at the semiconductor electrolyte interface can help to separate photogenerated e /h 1 couples, effectively suppressing recombination. When a semiconductor is brought into contact with an electrolyte, the electrochemical potential of the semiconductor (corresponding to the Fermi level, Ey of the solid [50]) and of the redox couple (A/A ) in solution equilibrate. When an n-type semiconductor is considered, before contact the Ey of the solid is in the band gap, near the conduction band edge. After contact and equilibration the Ey will... 

As shown in Eig. 3, the measured resistance R c in the depletion regime can reach several Mf2cm, but Eq. (12) indicates that it becomes equal to the effective resistance of the substrate which is less than 1 cm at the fh potential. Then the term l// sc is almost equal to zero under the depletion regime, and suddenly rises very sharply to almost infinity when the potential approaches the fb value (Fig. 4). This effect is extremely useful for a simple determination of the fb potential, which is found near OVvs. SCE, for p-type Si in a 5% HF aqueous solution. The procedure seems more rigorous, because it does not deal with an extrapolation method, and, owing to the sharp variation of the conductance, it needs just a few impedance measurements in the immediate vicinity of the fb potential. This method of investigation of the space charge layer, which reveals the formation of a depletion layer that is several Mf2 resistant, leads... 

The model suggests that at higher voltages the electron and hole currents in PPV-based devices with low contact barriers (as expected for selective Ohmic contacts) are determined by the bulk conduction properties of the polymer and not by the injection properties of the contacts. The conduction of holes is governed by space-charge effects and field dependent mobility, while electron transport is limited by traps. 

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