Chemistry Reference
In-Depth Information
hydrogen is the decisive factor for the anisotropic growth and passivation of macro-
pore side walls.
Large pores tend to have less anisotropic effect and grow more dominantly in the
direction of carrier supply, namely, perpendicular to the surface. On the other hand, for
pores of extremely small diameters, on the order of a few nanometers, the direction of
individual pores is not well defined. The macropores formed on
generally have
smooth walls and an orientation toward the source of holes that is perpendicular to the
surface even on (110) and (111) samples.
177,1027
Depending on the orientation of the substrate and formation conditions, the cross
section of individual pores may have different shapes as illustrated in Fig. 8.19(1),
p
-Si
