SILICON NONAQUEOUS SOLUTION INTERFACE STUDIED BY CAPACITANCE VOLTAGE AND CONDUCTANCE VOLTAGE TECHNIQUES

The capacitance-voltage and conductance-voltage techniques are applied to the study of the silicon-acetonitrile and silicon-methanol interfaces. The flat-band potential of the silicon electrode in these solutions shows an irreversible anodic shift during successive sweeps of the electrode potential, the amount of the shift depending on the electrolytes, the solvents, and the potential sweep regions. XPS spectra show that a silicon oxide layer is formed after the potential sweeps, and cations of the electrolytes are included in the oxide layer. This cation inclusion causes a potential drop across this layer, enhancing the barrier height in the silicon. The capacitance and conductance peaks observed for the silicon electrodes immersed in these solutions are attributable more probably to minority carriers in the surface region than surface states. The time constant for the conductance peak is longer than 3 x 10(-2) s in the dark, while it decreases to approximately 2 x 10(-4) s under illumination due to an increase in the minority carrier generation rate in the silicon. In the presence of the redox couple in the solution, the minority carrier quasi-Fermi level at the surface coincides with the redox level in the small bias region, and the linear Mott-Schottky plot arises.