Chemistry Reference
In-Depth Information
where
is a constant. Also, there is a power law relationship, existing
between pore diameter and doping concentration for the formation of stable pores (deep
pores without pore branching or dying).
Variation from Surface to Bulk.
The pores at the surface are smaller than those
in the bulk of PS as, for example, shown in Fig. 8.26.
8,37,40
Such an increase in pore
diameter from the surface to the bulk is due to the transition from pore initiation to
steady growth. Also, the walls of macropores may be covered with a layer of micro-
pores, i.e., two-layer PS, on illuminated
A
or on very lowly doped
p-
Si. On illumi-
nated
n-
Si samples, a micro PS layer exists on the surface of the large pores
n
-Si
