Structural and Optical Characterizations of Cadmium Chalcogenide Layers on Polyamide Formed Using Monotelluropentathionic Acid

Abstract

Mixed cadmium tellurides–cadmium sulfide thin layers were formed on the polyamide PA 6. Monotelluropentathionic acid (H2TeS4O6) was used as a precursor of tellurium and sulfur. A low-temperature, nontoxic, and cost-effective SILAR method was applied. Cadmium telluride (CdTe) and sulfide (CdS) layers were formed through the consecutive reactions of sorbed/diffused chalcogens species from telluropentathionate anion (TeS4O62−) with functional groups of polyamide and alkaline cadmium sulfate. The pseudo-second-order rate and Elovich kinetic models were the best fit to quantify an uptake of chalcogens and cadmium on PA 6. The effects of chalcogens and Cd on the structure and optical properties of PA 6 were characterized using UV-Vis and IR spectra. The clear changes of these properties depended on the concentration and exposure time in the precursor solutions. Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy were applied in order to evaluate the effect of the chalcogen species on the changes in structure of polyamide 6 films, depending on the exposure time in the solution of the chalcogens precursor and its concentration. The optical bandgap energy of the formed layers was found to be in the order of 1.52–2.36 eV. Studies by scanning electron microscopy and atomic force microscopy reveal that the diameter of the average grain is approximately 30 nm. The grains are conical in shape and unevenly distributed all over the surface of the substrate.