Chemistry Reference
In-Depth Information
bonded hydrogen before and after the replacement is not changed in both solutions.
The important difference is that after being terminated by a ion, the silicon atom
is a radical with two extra electrons, whereas in Si-F termination the bonds associated
with the silicon atom are neutralized.
The hydrogen adsorption onto a silicon atom is a reduction process since the
valence of the hydrogen atom is changed from +1 to 0. It occurs when the back bond
of Si-SiF or Si-SiOH is broken by reacting with or HF. Transfer of one electron
from the Si-OH bond to the hydrogen of the Si-H bond must then occur as illustrated
in Fig. 5.69. An important feature of this process is that no carriers from the solid are
involved, and thus this reaction is chemical in nature. This is the key reaction step
responsible for the chemical character of the dissolution process in that a hydrogen ion
