Chemistry Reference
In-Depth Information
the formation of anodic oxide on silicon.
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Even in “dry” solution the oxidation
depends on the water initially present as an impurity, or the water resulting from oxi-
dation of NMA. The amount of water in the solutions closely correlates to the growth
rate, the critical growth thickness, and the breakdown potential of the oxides.
228
The
effect of water on oxide growth in ethylene glycol is shown in Fig. 3.7. Figure 3.8
shows the maximum attainable voltage for anodization in ethylene glycol electrolyte
as a function of water content. The maximum voltage is above 350 V for water content
of less than 25% but is less than 150 V for water content of more than 30%. Water has
a similar effect on other solvents.
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It also has a significant effect on current efficiency.
Figure 3.4 shows that current efficiency is lowest for water content of about 1-2% in
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In
both NMA and glycol solutions.
ethylene glycol solutions,
