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Two types of etch pits in cadmium telluride have been observed. The etchants used are nitric acid solutions of potassium bichromate which also contain silver ions of various concentrations. The etch pits resulting from etch (EAg-1) grow into a tetrahedral shape bounded by the crystallographic habit planes and reveal geometrical polarity on the (111) and (1̄1̄1̄) surfaces. Another type of etch pit is formed at a different point from that of the pit with EAg-1 by the modified etch (EAg-2), which has increased content of Ag+ ion. The two types of etch pits, with EAg-1 and with EAg-2, are believed to be associated with Cd and Te edge dislocations. The dissolution rate and its selectivity to the constituent elements in cadmium telluride is controlled electrochemically by the variation of the Ag+ ion concentration of the etching solution. The structure of the twin boundary is also studied by etching and back Laue techniques.

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In the study of electroless Ni plating of Si wafers with p‐n junctions using conventional solutions, a pronounced difference in plating rate between p‐ and n‐type surfaces is observed. Further experiments show that rate difference probably should not only be attributed to the photovoltaic effect generated at the p‐n junctions but also to the electronegativity difference between p‐ and n‐type Si. The latter effect can be changed by addition of such material as NH4SCN or 2NH4‐EDTA to the plating solution. Whereas SCN− addition increases the rate difference, EDTA addition decreases it. This fact which can be put to practical use gives an extra support for the explanation given above.