Chemistry Reference
In-Depth Information
schematically illustrates the relation among the different potentials and energy levels.
The conduction band edge is related to the flatband potential according to the follow-
ing equation
Therefore, by measuring the flatband potential at pzc, one can determine the energy
level of the semiconductor band in an electrolyte relative to the absolute scale or the
vacuum scale. The pzc of a silicon electrode in aqueous electrolyte is similar to that of
at about pH 2.2, since the silicon surface is generally covered with a thin layer
716,903
of oxide.
1.3. POTENTIAL AND CHARGE DISTRIBUTION IN SPACE CHARGE LAYER
1.3.1. Carrier Density in Space Charge Region
The charge distribution within the space charge layer can be quantitatively
described by the Poisson equation:
where
x
is the distance from the surface and and are the donor and acceptor den-
sities, respectively. The electron and hole densities,
n
(
x
) and
p
(
x
), in the absence of a
current, follow the Boltzmann distribution:
962
