Chemistry Reference
In-Depth Information
One reason for the variation of properties from the Si/oxide to oxide/electrolyte
interfaces is that some silicon atoms in the anodic oxides are not fully oxidized. Figure
5.47 shows that a current peak occurs during the etching of the anodic oxides which
are formed on illuminated
The partially oxidized silicon atoms have relatively
high energy levels and are capable of injecting electrons into the conduction band and
generating a current at the end of the oxide dissolution. The position of the current peak
increases with decreasing HF concentration and with increasing anodic potential indi-
cating that the partially oxidized silicon atoms are concentrated near the silicon/oxide
interface. The occurrence of this anodic current during etch-back in HF solutions is
general for essentially all anodic oxide films formed in HF solutions as well as in alka-
line solutions on both types of materials.
74,286,602
The amount of charge associated with
the partially oxidized silicon atoms, up to an equivalent of several monolayers of Si
3+
,
74
n
-Si.
