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Surface microstructure, optical and electrical properties of spray pyrolyzed PbS and Zn-PbS thin films for optoelectronic applications

Abiodun E. A., Emmanuel A., Bidini A. T., Enoch D. O., Omotoso E., Adeyemi O., Babatunde O. G.

Materials Science Poland

2017

Vol. 35, No. 3

576--582

Lead sulphide (PbS) and zinc- doped lead sulphide (Zn–PbS) thin films were prepared by chemical spray pyrolysis on soda lime glass substrates at a temperature of 250 °C. Precursors were prepared from chemical reagents including zinc acetate, lead acetate and thiourea. The deposited films thicknesses and elemental composition were studied by Rutherford backscattering spectroscopy (RBS); the percentages of Pb and S were estimated as 40.58 % and 59.42 %, respectively, while for the Zn-doped sample, the percentages of Zn, Pb and S were respectively 4.84 %, 44.57 % and 50.59 %. Morphological studies revealed that the films were continuous and the particles were uniformly distributed across the substrate surface. AFM probe revealed nanostructured films with particles densely distributed across the substrates surfaces with incorporation of Zn2+. Statistical distribution of the grains over a specific projected area indicated average growth height of about 47 nm. Optical studies indicated that the transmission in visible light region of Zn-PbS thin film was superior to that of the undoped sample. Interband transition of both PbS and Zn-PbS films is directly allowed and their energy band gaps were found to be 0.43 eV and 1.45 eV, respectively. Electrical characterization showed that both films are of p-type conductivity with surface resistivity values of the order of 104Ω·cm.

Metal-organic chemical vapour deposition of lithium manganese oxide thin films via single solid source precursor

Oyedotun K. O., Ajenifuja E., Olofinjana B., Taleatu B. A., Omotoso E., Eleruja M. A., Ajayi E. O. B.

Materials Science Poland

2015

Vol. 33, No. 4

725--731

Lithium manganese oxide thin films were deposited on sodalime glass substrates by metal organic chemical vapour deposition (MOCVD) technique. The films were prepared by pyrolysis of lithium manganese acetylacetonate precursor at a temperature of 420 degrees C with a flow rate of 2.5 dm3/min for two-hour deposition period. Rutherford backscattering spectroscopy (RBS), UV-Vis spectrophotometry, X-ray diffraction (XRD) spectroscopy, atomic force microscopy (AFM) and van der Pauw four point probe method were used for characterizations of the film samples. RBS studies of the films revealed fair thickness of 1112.311 (1015 atoms/cm2) and effective stoichiometric relationship of Li0.47Mn0.27O0.26. The films exhibited relatively high transmission (50 % T) in the visible and NIR range, with the bandgap energy of 2.55 eV. Broad and diffused X-ray diffraction patterns obtained showed that the film was amorphous in nature, while microstructural studies indicated dense and uniformly distributed layer across the substrate. Resistivity value of 4.9 Omega.cm was obtained for the thin film. Compared with Mn0.2O0.8thin film, a significant lattice absorption edge shift was observed in the Li0.47Mn0.27O0.26film.