Probe Beam Deflection Study of p-Si Electrodissolution in Acidic Fluoride Medium in the Oscillating Regimes

The 'mirage' or probe beam deflection (PBD) technique has been used to investigate Si dissolution in acidic fluoride in the regime of electropolishing, in which the electrode surface is covered by a thin oxide film. During current oscillations at a constant applied potential, the variations of the dissolution rate basically reflect variations in the rate of oxide film formation. During potential oscillations at a constant imposed current, the dissolution rate varies with the same periodicity as the potential, with a maximum when the potential is low and a minimum when it is high. Results indicate a correlation between physico-chemical and electronic properties of the oxide film, which appears more prone to etching in its less passivating form and vice versa.