Chemistry Reference
In-Depth Information
(100) orientation relative to that of the (111) orientation.
2,38
Figure 8.3 shows
i-V
curves
of different types of Si in 1% HF solution. Except for a shift along the potential axis,
which reflects the difference in the Fermi levels of these materials, the
i-V
curves
of
p
type and heavily doped
n
types are largely identical.
The
i-V
curves on non-heavily doped
n
-Si are shown in Fig. 8.4. Unlike
p
and
heavily doped
n
-Si, a much larger anodic polarization is required to generate the dis-
solution reaction in the dark; the lower the doping level, the higher the applied poten-
tial for a given current density.
2
Also, the
i-V
curves may not show the clearly defined
regions as on other types of Si, but depend on measurement procedures. As shown in
Fig. 8.4 the
i-V
curve with a positive potential scanning rate is different from that with
a negative scanning rate; different regions are revealed only on the curve measured at
a certain negative scanning rate. As will be discussed later, it is the particular reaction
and the morphology that give rise to the
i-V
characteristics shown in Fig. 8.4. Also,
the current flow on
n
-Si is very sensitive to surface roughness.
9,42
Mechanical
-Si
