Chemistry Reference
In-Depth Information
surface is at a reduced state with a valence of 0. The lattice silicon atoms bonded to
hydrogen atoms also have a valence of 0 (or four valence electrons). The silicon atoms
on the surface which are bonded to one hydroxyl ion or one fluoride ion, on the other
hand, have a valence of +1.
Elemental Steps.
The dissolution of a surface silicon atom involves first the
replacement of the surface hydrogen atom by a in KOH solutions and by in HF
solutions. The difference between the hydrogen replacement by and is whether
holes are involved. As shown in Fig. 5.68, in KOH, on the hydrogen replacement by
the silicon atom becomes a radical, which in the following reaction steps is neu-
tralized by the reduction of hydrogen ions. In HF, the replacement of hydrogen by
requires a hole which results in a neutralized Si-F bonding. The valence state of the
