Formation of Ordered, Nonreconstructed CdTe ( 111 ) Surfaces Electrochemically: Studies by LEED and Auger Electron Spectroscopy

Abstract

Surface treatments for single crystals have been examined to determine procedures which result in the formation of ordered stoichiometric surfaces, reflecting a truncation of the bulk crystal structure. Nonreconstructed surfaces were obtained in solution using a etching solution followed in sequence by a sulfuric acid rinse and electrochemical reduction. The etching procedure leaves a disordered Te layer and etch products such as . By rinsing in , the can be removed leaving only the Te layer. Subsequent electrochemical reduction converts the Te layer to telluride ions, which are soluble. Low energy electron diffraction (LEED) and Auger electron spectroscopy were used to characterize the surfaces. Ordered (1X1) LEED patterns and stoichiometric surfaces were observed following the procedure just described. Variations in the intensity distributions between spots in the (1X1) LEED patterns for the (111)Cd and (111)Te surfaces were significant enough to provide a clear means of differentiating the two faces. Vacuum studies where ion bombardment has been used to clean surfaces generally result in damaged surfaces, which can be repaired by subsequent annealing. The (111)Cd surface following annealing displays a (2X2) LEED pattern, the result of a surface reconstruction. The (111)Te displays a complex LEED pattern indicative of the formation of pyramid‐shaped facets. Another etching solution consisting of , , and was also investigated but proved too severe; the resulting Te layer was thicker than the one formed in and was difficult to remove. Surface heterogeneity appears to have been introduced by this etching process as well.