Chemistry Reference
In-Depth Information
native oxide film in nonfluoride solutions or surface termination by hydrogen in HF
solutions.
In nonfluoride solutions such as KCl, HCl, and the dark limiting current
on well-prepared samples (relatively few defects) is on the order of several microam-
peres per square centimeter, which is much higher than the bulk diffusion current.
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The origin of the large current is related to the surface states arising from adsorption
or reaction intermediates, which is strongly affect by the presence of oxide on the silicon
surface. Figure 5.24 shows that the surface covered with an oxide has a limiting cur-
rent several orders of magnitude smaller than that on an oxide-free surface. It also
shows that an initially oxide-free surface, when in contact with the aqueous electrolyte,
is quickly covered by an oxide resulting in a decrease of the dark limiting current.
According to Chazalviel,
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the transient current shown in Fig. 5.24 may be described
by
