Hydrogen-depleted layer

Figure 1. Carbon abundance as a function of mass for both components of a close binary system at the onset of mass transfer. The region from Mx=0 to Mr=Mgi=8.1 Mo corresponds to the originally less massive component (gainer), whereas the carbon distribution of the loser is plotted from 8.1 Mo (surface) to 17.1 M (center). The first occurrence of hydrogen depleted layers (Xat<0.7) and the end of the Roche Lobe Overflow are indicated.

The usual picture of cationic chemisorption on a p-type semiconductor is that an electron is transferred from the foreign atom to an impurity level in the solid. The foreign atom is converted to the cation, and a depletion layer is built up in the solid. This occurs in the and C(PAfR regions of Fig. 7, provided that the SJl level lies above the impurity levels. In this case, the ASJl level is vacant and a hydrogen-like foreign atom exists on the surface as the cation. 

Another possible effect of PdAu deposits on PdAu/SnOx sensors is through the formation of a Schottky barrier between PdAu and SnOx, as in the case of the Pd/CdS hydrogen sensor. If such a barrier is formed, then a depletion layer is created inside the semiconductor tin oxide. Since the Pd work function can be reduced by hydrogen absorption through dipole or hydride formation (14,15), the width of the depletion layer in tin oxide may be reduced. The reduction of the depletion layer width causes the sample resistance to decrease. Such a possibility was checked and was ruled out, because a good ohmic contact was obtained between Pd (-50 nm thick) and SnOx- It is also commonly known that gold forms an ohmic contact with tin oxide. 

In the case of dilute acid solutions (pH >2), the alkalis and basic oxides are dissolved preferentially, but the amount of silica dissolved is less than that removed by water alone ( 7, , ). This can be explained by the fact that the acid neutralizes the leached alkalis, so that the pH does not rise to higher values where silica dissolution becomes important. The preferential leaching produces an alkali-depleted layer that can be twice as thick as the one obtained by neutral water (10). Because of the replacement of the alkali ions by the smaller hydrogen ions, stresses will be induced in this layer which can cause it to crack. Further shrinkage can also occur if this hydrated silica layer loses water (10,11). 

Fig. IV.16 shows photocurrent voltage curves for hydrogen evolution at such electrodes. One sees that the hydrogen evolution even under illumination begins at these electrodes just at the reversible hydrogen potential and not at much more anodic potentials where according to the theoretical expectations a depletion layer should begin to be formed. The figure shows a theoretical curve for such...

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