Etching nonaqueous solutions

The specifics of the degradation phenomena define the electrode pretreatment. In the case of mechanical treatment, the surface composition can vary due to heating [60], and this can be avoided by polishing in nonaqueous solutions [47] or by slowly cutting the surface layer while it is out of contact with air. Chemical treatment [60,61] will be discussed below in the context of the HTSC etching problem. 

Very little has been published on the electrolytic etching of semiconducting materials other than germanium and silicon. There probably have been many unpublished small experiments carried out to determine a suitable electropolishing process for many of the intermetallic semiconductors. Uhlir (36) for example, found that a largely nonaqueous HF solution suitable for electropolishing silicon would also electropolish GaSb. 

Another model proposed by Kohl and coworkers [77, 78] is based upon the strain - induced preferential etching described earlier. The model accounts for the formation of macropores and highly branched micropores when the silicon is rendered porous in either nonaque-ous or aqueous HF solutions, respectively. 

They suggest that the contrast between aqueous and nonaqueous etching can be attributed to two factors, the competition of OH with F for complexing Si, and the kinetically slow dissolution of oxide (or hydroxide) species formed in aqueous solutions. 

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