Analytical TEM study of CdTe layer electrodeposited from basic ammoniacal aqueous electrolyte

The nanoscaled local compositions of a polycrystalline cadmium telluride (CdTe) layer electrodeposited from a basic ammoniacal aqueous electrolyte were investigated by nanoprobe energy dispersive spectroscopy (EDS) combined with high-resolution transmission electron microscopy (TEM). The macroscale-averaged composition of electrodeposited CdTe layers is usually rich in Te by similar to1 atom % compared to the stoichiometric composition. Since the potentials applied for electrodeposition of CdTe are positive to the Nernst potential for elemental Cd deposition and are negative to that for elemental Te, the electrodeposited CdTe layers are suspected to comprise a small amount of elemental Te as a second phase. Elemental mapping of the CdTe layer using nanoprobe EDS revealed, however, that both Cd and Te are distributed uniformly in the entire layer; the nanoscaled chemical compositions at grain boundaries and triple-junctions are the same as those of bulk CdTe grain interiors. These results indicate that the electrodeposited layer is single-phased CdTe which forms a solid solution with excess Te. (C) 2004 The Electrochemical Society.