Enhanced anodic Si dissolution in water-ethanol acid fluoride media

The anodic behaviour of p-Si electrodes is investigated in water-ethanol media by rotating disk voltammetry. The water-alcohol media, in comparison to water, lead to (i) distorted current-potential curves, with a comparative current growth in the region of low applied potentials, (ii) a shift from about pH 3 in water to about pH 4 in 50% ethanol v/v of the maximum of the current-pH curves and (iii) a marked increase in dissolution current measured at pH > 2, with an opposite effect at pH < 2. The effect of ethanol on the current is discussed considering the modification of the speciation equilibria of hydrofluoric acid and possible effects on the kinetics of dissolution of the surface oxide layer.