Surface Morphology and Elemental Composition of Vernonia amygdalina-Sensitized Ternary Chalcogenide Thin Films: A Comparative SEM/EDS Study of CdZnS, ZnSnS, ZnCdSe, CuZnS and CuZnSnS

Abstract

The surface morphology and elemental composition of five solution-grown ternary chalcogenide thin films – cadmium zinc sulphide (CdZnS), zinc tin sulphide (ZnSnS), zinc cadmium selenide (ZnCdSe), copper zinc sulphide (CuZnS) and copper zinc tin sulphide (CuZnSnS) – were examined after sensitization with a natural dye extracted from Vernonia amygdalina (bitter leaf), using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). SEM micrographs of all five dye-sensitized films revealed continuous, grain-covered surfaces consistent with solution-grown chalcogenide films. EDS confirmed the presence of the expected metal and chalcogen constituents in each film – Cd, Zn and S in CdZnS; Zn, Sn and S in ZnSnS; Zn, Cd and Se in ZnCdSe; Cu and Zn and S in CuZnS; and Cu, Zn, Sn and S in CuZnSnS – together with carbon and oxygen attributable to surface adsorbates and dye-related organic residues. The combined oxygen and carbon content varied widely across the series, from 59.4 at.% in CdZnS to 84.4 at.% in ZnCdSe, with ZnSnS, CuZnS and CuZnSnS falling between these extremes, indicating substantially different degrees of dye-related surface coverage on the five host lattices despite identical sensitization conditions. These results confirm successful elemental incorporation of the intended ternary compositions in all five systems and demonstrate that the extent of bitter leaf dye attachment, as judged by surface C and O content, is strongly host-dependent.