Effect of Polarization Conditions

Anodization can be carried out under different modes with constant potential (potentiostatic mode) or constant current (galvanostatic mode). Constant potential means that the oxide grows under different field strengths from the start to the end of anodization, whereas constant current means that the oxide grows under a constant field. Most studies on the anodization of silicon employ the galvanostatic mode. 

The formation of oxide depends on the rate at which the voltage is applied as well as the area of the electrode surface under a constant potential mode. The mechanism by which the first few layers of oxide are formed is important in establishing the mechanism of growth of the entire oxide film. 

FIGURE 3.11. Oxide thicknesses as a function of applied potential for both COSI and ramped (lOOmV/s) growth modes. The growth time was 30 min. The substrates were (100) p-type Si with a resistivity of 3 to 7 flcm. The electrolyte used was O.IM HCl. After Bardwell et al (Reproduced by permission of The Electrochemical Society, Inc.) 

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Ingold, Edith Hilda. "The Correlation of Additive Reactions with Tautomeric Change. Pt. IV. The Effect of Polar Conditions on Reversibility." JCS 127 (1925) 469475. 

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