Etching on polar (111) surfaces of CdTe crystals studied with Auger electron spectroscopy

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Abstract
Various reducing and oxidizing etches were applied to the polar (111)Cd and (111)Te surfaces of CdTe crystals. The induced surface layers were studied with Auger electron spectroscopy, and the chemical reactions involved were discussed. A dithionite etch left both (111) Cd and (111)Te surfaces Cd rich. The sulfur in the etch solution appeared to replace Te in the near surface. A hydrazine etch left the Cd to Te ratio about one to one on the surfaces. A large oxygen peak was observed to increase as the etching time and temperature increased, indicating that the etch was not reducing. Hydrogen heat treatment left the surface stoichiometric, free of contamination and crystalline. Hydrogen heat treatment was the best method we have tried to retain the stoichiometry of the (111)CdTe surfaces. The surfaces treated with oxidizing EAg-1 solution were Te rich, and the strong correlation between the relative concentration of Te and Ag suggested a reaction between Te and Ag. The Te(NOO)/Te(MNN) ratio on (111)Te surfaces was always significantly higher than that on (111)Cd surfaces after hydrogen heat treatment or sputter cleaning consistent with the crystallographic polarity we reported previously.