Formation of Thin Films of CdTe, CdSe, and CdS by Electrochemical Atomic Layer Epitaxy

Abstract

Thin films of CdTe, CdSe, and CdS have been electrodeposited by electrochemical atomic layer epitaxy (ECALE), using an automated electrochemical deposition system. Previous reports of an automated system for forming ECALE deposits involved use of a small thin layer flow cell, which revealed several drawbacks. Conversion of the thin layer cell to a thick layer design resulted in greatly improved deposit quality and reproducibility. Deposits were analyzed using electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and grazing incident X‐ray diffraction (XRD). The results were consistent with a layer by layer growth mode and the principles of atomic layer epitaxy. CdTe films were grown using up to 1000 ECALE cycles, and were stoichiometric through 500. The 1000 cycle films were a few percent rich in Te, under the conditions used. CdSe and CdS films formed also contained some excess chalcogenide, probably the result of less then ideal deposition parameters. Increasing amounts of particulates and surface roughening were observed for the 500 and 1000 cycle CdTe and CdSe films, relative to the 200 cycle deposits normally formed. This roughening may result from the excess chalcogenide. XRD of the films indicated cubic crystal structures with preferred (111) orientations for all three compounds.