Chemistry Reference
In-Depth Information
hydrogen, increasing the fluoride concentration increases the number of Si-F bonds
and the dissolution intermediates capable of transferring charge into the conduction
band. Figure 5.28 shows the effect of pH on the dark current in fluoride solutions.
The current is the lowest at pH 10 when silicon oxide is the most stable in the HF solu-
tion. The dependence of dark current on pH is similar for (111) and (100) surfaces as
shown in Fig. 5.29, but that on the (100) surface is about 1.5 times higher than the (111)
surface.
95,904
Large dark current may also be generated by interface tunneling due to the pres-
ence of oxidizing species. For example, Fig. 5.30 shows that the dark current on the
silicon electrode in NH
4
F increases with Br
2
concentration.
11
According to Gerischer
