Gas-Sensing Properties of Cu2+-Doped CdxPb1 − xS Thin Films

Copper(II)-modified polycrystalline films of CdxPb1 − xS substitutional solid solutions (B1 cubic structure, space group Fm3̄m ) were prepared by chemical bath deposition. It was shown that copper(II) ions in the bath can act either as an activator or as an inhibitor during formation, depending on their concentration. Therefore, Cu2+ ions affect the film thickness and morphology, elemental and phase composition, texturing, and gas-sensing properties. The maximum response (at 1120 ppm ammonia) of the Cd0.057Pb0.943S/Cd0.078Pb0.922S/Cd0.101Pb0.898S three-phase film was due to its increased homogeneity, high average texture index, and the presence therein of copper, which formed strongly bonded complexes with ammonia, and surface sulfonyl and carbonyl groups identified by IR spectroscopy, which performed as active adsorption centers. We proposed the scheme to describe the interaction of ammonia with the surface of Cu2+-modified CdxPb1 − xS films at room temperature.