Composition of Oxide Layers

Another mechanism is involved in the Cu(II)-containing solutions where Cu+ ions are generated due to the interaction between Cu and the metalhc phase of the copper electrode 

The latter process attains equilibrium, if the Cu concentration does not exceed some critical (maximum) value specified by the relation [30] 

Otherwise, an excess of Cu+ ions will react with OH yielding CU2O. The net 

3) and (10.5) refer to the main relationships that determine the conditions for formation of stabile CU2O. 

The largest amount of oxygen was found on the surface of all the samples this being the result of oxidation in the atmosphere. This surface layer is very thin (1 - 2 nm) and is easily removed by sputtering. The subsequent distribution of oxygen depends on the thickness of the oxide layer. As will be seen next, oxide layers may be destroyed to a large extent when the appropriate negative polarization is applied. 

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SIMS analysis as carried out in our previous work [12,39] provides a qualitative analysis of Cr enrichment of the surface. Based on such qualitative analysis of Cr content, a Cr203 oxide layer was proposed to develop in nanocrystalline alloy, whereas, it was proposed that a mixed Fe-Cr oxide layer forms in case of microcrystalline alloy. A Future study quantifying the Cr, Fe and O contents of oxide layer and their oxidation states using techniques such as X-ray photoelectron spectroscopy (XPS) must provide a better understanding of the effect of nanocrystalline structure on the chemical composition of oxide layer. 

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