Polarization and Photopotentials of InSb in NaOH

The anodic dissolution of the (111)-Sb surface in 1 N NaOH was at a slightly higher rate compared to the (111)-In surface. On the other hand, the rate of hydrogen evolution was slightly higher on (111)-In than on (111)-Sb. Anodic dissolution was not affected by illumination prior to passivation. However, photopotentials as high as 0.1 V were observed after the InSb was anodized at passivating currents. The magnitude of the photopotentials decreased during the potential decay after anodization was completed. The spectral response of the photopotentials after attainment of steady state corrosion potentials was determined. The differential capacitance at the corrosion potential prior to anodization was 35 μF/cm². Immediately after anodization, the capacitance was 0.6 μF/cm² and then increased to about 2.2 μF/cm² at the end of the potential decay. Both the photopotentials and small capacitance values were due to the film formed during anodization.