Chemistry Reference
In-Depth Information
thermal oxide on silicon in NaCl solutions) the surface states may also arise by surface
adsorption by and ions at the oxide/electrolyte interface.
902
In at pH 9, extra capacitance over that of the space
charge layer is observed at potentials between -0.7 and in the dark as shown
in Fig. 2.26.
93
The peak is at and disappears at frequencies above 20 kHz. This
peak is attributed to the reversible charge exchange between monoenergetic interface
states and the conduction band. The density of the interface states is determined to be
and its energy is located 0.36 eV from the conduction band edge.
Under illumination the capacitance as a function of potential reveals two maxima at
-0.3 and as shown in Fig. 2.27. The two maxima are found to occur at all light
intensities and their positions vary with light intensity and frequency. According to
Oskam
et al
.,
93
the peak at represents the same interface states as in the dark
but with a higher density of The density of these states at
increases with photocurrent density and is on the order of to The
surface states that responsible for the recombination are produced under illumination
and are likely to be associated with oxidation intermediates. Surface states of similar
