R. Mariappan

Effect of solvent and substrate temperature on morphology of cerium oxide thin films by simple nebuliser spray pyrolysis technique

Abstract Cerium oxide thin films are coated on glass substrates by nebuliser spray pyrolysis technique. The crystallographic structures, surface morphology, optical properties and I–V characteristics have been studied as a function of solvent and substrate temperature (300–500°C). X-ray diffraction was used to estimate crystallographic texture, grain size, strain and lattice constant. All films exhibit cubic fluorite structure with different preferred orientations depending on the preparation conditions. Photoluminescence spectra revealed the presence of violet and blue emissions in the visible region. The calculated band gap energy is found to be in the range 3·0 to 3·6 eV. Spherical and lamellar shaped particles with crystallite size 10–41 nm are found in the film surface. X-ray photoelectron spectroscopy analysis confirms the highly non-stoichiometric nature of the films with dominant occurrence of Ce4+ (CeO2) and subsidiary occurrence of Ce3+ (Ce2O3).

Effect of ammonia solution on properties of sprayed ZnO thin films consisting of nano-pyramids

Hexagonal wurtzite zinc oxide (ZnO) thin films were deposited at substrate temperatures from 300 to 500 °C with surfactant of ammonia solution. The effect of ammonia on the structural, surface morphology, compositional, optical and electrical properties of ZnO thin films was studied. X-ray diffraction shows that the all films are polycrystalline in nature and have a hexagonal wurtzite structure with a high preferential orientation (002) plane for ammonia solution. High-resolution SEM studies reveal the formation of ZnO films consisting of nano-pyramids with uniformly distributed grains over the entire surface of the substrates. Photoluminescence studies indicate the presence of two emission peaks: (a) a sharp ultra-violet near band edge ∼392 nm, (b) a sharp visible deep-level green emission peak ∼564 nm. The optical properties show that the direct band gap energy values increase with increasing substrate temperatures.

DBSA doped polypyrrole blended with Poly(4-styrenesulfonic acid) by mechanical mixing

DBSA doped polypyrrole was prepared by In-situ chemical oxidative polymerization method. The reaction temperature was 0 to 20 °C. Different weight percentages of PSS (40 wt.%, 60 wt.% and 80 wt.%) were mechanically blended with a pestle in an agate mortar for 25 minutes by solid state mixing. The investigation of the blend focused on the optical, structural and morphological properties. SEM micrographs indicated that PSS was homogeneously distributed within DBSA doped PPy. FT-IR study confirmed the doped and blended dopants in the composite structure. UV-study revealed the π → π* transition in benzenoid rings of DBSA and presence of PSS. The semi-crystalline nature of the composites improved with increasing the weight percentage of PSS.