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Author: search.filters.author.Veena, E.Has files: No

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    Effect of substrate temperature on the structural and electrical properties of spray deposited lead sulfide thin films
    (Elsevier Ltd, 2016) Veena, E.; Bangera, K.V.; Shivakumar, G.K.
    Lead sulfide (PbS) thin films were prepared by chemical spray pyrolysis method using lead acetate and thiourea as precursors of Pb+2 and S-2 ions. X-ray diffraction (XRD) technique, scanning electron microscope (SEM) and EDAX analysis were used for structural, morphological and compositional characterization. XRD analysis shows that the films are cubic in nature with a preferred orientation along (2 0 0). EDAX analysis shows that films deposited at 150°C are sulfur rich. An increase in the substrate temperature results in a decrease in the sulfur content of the prepared film. It has been observed that thin films deposited at or above 225°C are smooth & uniform morphologically. Beyond a substrate temperature of 275°C, the films become discontinuous and non-uniform. However, the films are sulfur rich, even at 275°C. Electrical conductivity of prepared thin films have been measured using silver contacts in coplanar geometry. Films are n - type as confirmed by hot probe technique. The electrical conductivity at room temperature (25°C) was in the order of 10-4 Ω-1cm-1 and was found to increase with increase in temperature showing the semiconducting nature of the films with the band gap of 0.39 eV. © 2016 Elsevier Ltd.
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    Influence of zinc precursor concentration on properties zinc sulphide thin films using spray pyrolysis technique
    (American Institute of Physics Inc. subs@aip.org, 2017) Veena, E.; Bangera, K.V.; Shivakumar, G.K.
    Stoichiometric high transparent n-zinc sulphide thin films were prepared using chemical spray pyrolysis technique. The concentration of the cationic precursor played a major role to obtain stoichiometry, regardless of various deposition parameters. Zinc sulphide films deposited at 450?C for the ratio 0.33:1 (Zn:S) resulted in well oriented, stoichiometric polycrystalline cubic structure. The variation in crystallite size associated with the cationic precursor concentration provides significant control over the structural, optical and electrical properties of the films. The optical band gap and activation energy of stoichiometric ZnS films were found to be 3.54 ± 0.02eV and 0.82 ± 0.05eV, respectively. The absorption coefficient of the films was found to be 102 cm-1. © 2017 Author(s).
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    Effect of annealing on the properties of spray-pyrolysed lead sulphide thin films for solar cell application
    (Springer Verlag service@springer.de, 2017) Veena, E.; Bangera, K.V.; Shivakumar, G.K.
    Annealing is the most important processing parameter perhaps as it directly affects the properties of the thin films. In the present article, lead sulphide thin films composed of (2 0 0) plane-oriented nano-rods were successfully synthesized on glass substrates using spray pyrolysis technique at annealing temperature 350 °C. Films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive analysis by X-ray (EDAX), UV–VIS–NIR spectrometry and two-probe experiments. The X-ray diffraction study confirmed that films exhibiting face-centred cubic structure with a preferred orientation along (2 0 0) plane were independent of annealing temperature. SEM photographs revealed the formation of nano-rods. The possible formation of nano-rods and its dependency on optical and electrical properties were discussed. Chemical composition in terms of atomic ratio of the constituents is determined from EDAX studies. The optical band gap of the lead sulphide thin films was found to decrease from 1.22 to 0.98 eV with an increase in annealing temperature. The electrical conductivity of the films at room temperature was of the order of 10?2 ??1 cm?1 with the low activation energy. Results prove that lead sulphide films grown by chemical method appeal its adoptability for potential solar cell applications. © 2017, Springer-Verlag Berlin Heidelberg.
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    Effective role of thickness on structural, electrical and optical properties of lead sulphide thin films for photovoltaic applications
    (Elsevier Ltd, 2017) Veena, E.; Bangera, K.V.; Shivakumar, G.K.
    The n-type lead sulphide thin films were deposited at 350 °C substrate temperature on glass substrates using advanced spray pyrolysis technique. The thickness of the thin films played an important role to improve the properties of lead sulphide and to use in device fabrication apart from various deposition parameters. The films deposited at thickness of 520 nm resulted in a well oriented polycrystalline with face-centered cubic structure. An enhancement in the crystallite size with increase in film thickness was evidenced by XRD and SEM. The variation in crystallite size of films associated with different thickness provides a significant control over optical and electrical properties. The resistivity of the thin films decreased with an increase in thickness was of the order of 102 ? cm. The activation energy and optical band gap of the films deposited at optimized condition were found to be 0.20 eV and 1.22 eV, respectively. The absorption coefficient of the films was found to be 106 cm?1. Results prove that the lead sulphide films synthesized using spray technique appeal its adaptability for potential photovoltaic applications in solar cells. © 2017
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    Study on structural, optical and electrical properties of spray pyrolysed PbxZn1-xS thin films for opto-Electronic applications
    (Elsevier GmbH journals@elsevier.com, 2017) Veena, E.; Bangera, K.V.; Shivakumar, G.K.
    Ternary thin films are attractive for many applications due to their band gap tunability. In the present study, the stoichiometric n-PbxZn1-xS (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1) thin films were deposited on glass substrates using spray pyrolysis technique. The structural, optical and electrical studies have been carried out in order to understand the band gap tunability of prepared films. The XRD analysis confirmed that the prepared films were polycrystalline in nature with cubic structure. The substitution of zinc into the lead sulphide lattice led to decrease in the crystallite size, and the orientation of the films changed from (200) to (111) plane. SEM images clearly showed a modification in the morphology of the films from nano size particle to network structure due to Zn ion substitution. The optical band gap energy of PbxZn1-xS thin films varied from 0.40 eV to 3.54 eV and the transition has been changed from indirect to direct with the substitution of zinc into the lead lattice site. The resistivity and activation energy of the films were increased with increase in the band gap. The results confirm the formation of a continues solid solution of PbS and ZnS in the ternary phase which can be a suitable candidate for optoelectronic applications. © 2017 Elsevier GmbH