Abstract Constant voltage anodization of silicon was carried out to grow thin silicon oxide layers on silicon. Four different forming solutions, i.e. ethylene glycol + 0.04(N) HNO 3, KNO 3, NH 4NO 3 and Ba(NO 3) 2 were used. Oxidation proceeds at the rate of 6 Å V −. The current decay consisted of one sharply and another slowly decaying exponential. Initially, growth is linear with time when the rate of growth of the oxide is maximum. This is followed by drastic deviation from linearity towards saturation. The ionic current efficiency is highest for the forming solution containing NH 4NO 3 and the best value for this solution is 0.88% at 80 V. The refractive index of these oxides was found to be 1.46. The oxygen evolution at the anode during oxidation and the current caused by this evolution were studied using gas chromatography. The electronic properties, viz. mobile charge, fixed charge and interface states density of these oxides were measured by capacitance-voltage techniques and the best values were obtained for the solution containing 0.04(N) NH 4NO 3.