Polishing and Isolating the Face of Interest

After cutting along the desired crystal face, the surface is left with a disturbed layer on top. The physical state of the electrode surface must be that of an atomically flat face described above (see Section 

Therefore the experimenter must try, by all means available, to create a disturbed layer as thin as possible, or absent. Elimination of this disturbed layer can be done either directly by electrochemical polishing (e.g., possible for silver) or by mechanical polishing, followed by electrochemical or chemical polishing. 

Any book of metallography provides good information for this step of preparation of the surfaces. 

The choice of the ingredients used for mechanical polishing (felt or cloth, alumina powder or diamond paste, etc.) is dictated by the hardness of the metal and its chemical properties. Soft metals (such as gold) are more difficult to polish than hard metals because the polishing material can possibly be buried into the metal and consequently modify the chemical composition of the electrode surface (see Section IV.6). 

Mechanical polishing is generally first done with fine emery paper. Care must be taken to work across the lines (scratches) formed on the surface by continual random rotation of the sample. Then alumina powders of different grades (on different felts) or diamond pastes of different grades (on different cloths) are used to remove, as well as possible, the disturbed layer.t A mirror finish should be observed for instance, no trace of the lines due to the polishing should appear when observation is magnified 20 times. 

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