The process of hole injection into the valence band of normaln‐normalGaAs from the oxidized component of redox couples in aqueous solution has been studied by means of the rotating ring‐disk system and by luminescence measurements as a function of electrode potential, mass transport, and electrolyte pH. It has been found that in all cases in which hole injection takes place, a luminescence signal is observed as a consequence of electron‐hole recombination. The intensity of this signal depends on the electron density at the interface (therefore on potential) and on the chemical composition of the electrode surface. The luminescence signal at cathodic bias demonstrates that electron transfer from the valence band is still dominating if the electronic energy levels of the redox species match the energy levels of the valence band, although electron transfer from the conduction band is energetically more favorable.

The growth and dissolution of oxide layers on silicon has been studied under illumination and in the dark by analyzing current transients at different voltages in solutions of NH4F of various concentrations at pH values between 1 and 4.5. When the oxidation rate of the silicon at high enough anodic bias and, for n‐type specimens, high enough illumination intensity exceeds the rate of oxide dissolution in the fluoride, the film grows until it has reached a thickness where the dissolution is rate‐determining for the net process. At higher voltages the current begins to oscillate. The data give some insight into the composition of the oxide layers and their electronic and ionic properties.

The electroreflectance signal from a semiconductor electrode surface is sensitive to the magnitude of the space charge. It is used to determine the voltage distribution between the space‐charge layer and the Helmholtz double layer at an electrode/electrolyte interface. In this paper, the first of two, we describe the experimental arrangements and measurements of the electroreflectance spectra for normaln‐MoSe2 and normaln‐WSe2 under anodic and cathodic bias. Important features in the spectra are found to be in agreement with existing theories. Flatband values inferred from the electroreflectance spectra are in agreement with those from Mott‐Schottky plots. The effects of Fermi level pinning on the electroreflectance spectra are demonstrated with normaln‐normalGaAs .

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