Electrode Reactions and Mechanism of Silicon Anodization in N-Methylacetamide

Abstract

The electrochemical processes occurring during anodization of low resistivity silicon were studied to determine the effect of electrolysis conditions on the rate and quality of oxide production. The rate of anodic formation us. water content in solutions was studied by means of ionic current efficiency, weight and analysis of silicon oxide. Current efficiencies of oxide production up to 3.0% were observed and the best oxides were formed at the lowest values of 1.6–1.8% The oxide formed corresponded within experimental error of method when Si was anodized in NMA solutions containing from about . At higher water content, the film weight increased with respect to stoichiometric as determined by silicon in oxide analysis. Thermally grown oxides showed a stoichiometric ratio (with some scatter); however, weight measurements of the silicon before and after thermal oxidation indicated that about 12% of the silicon consumed did not appear in the oxide formed. The mechanism proposed at this time suggests anodization of Si depends on the water formed during electrolysis of NMA. Hydrogen at the cathode is accompanied by formation. Oxygen containing electrolytes such as are not involved in the mechanism and are necessary only to increase solution conductivity. A solid secondary amide may be considered as the main anodic electrolysis product.