Faculty Publications
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Item Investigations on electrical properties of the CdxZn 1-xS thin films prepared by spray pyrolysis technique(2011) Raviprakash, Y.; Bangera, K.V.; Shivakumar, G.K.Thin films of CdxZn(1-x)S (0≤x≤1) were deposited on glass substrates by the chemical spray pyrolysis technique. The electrical properties of these films in relation with composition were studied in detail. The entire investigation was made for a wide range of compositions of CdxZn(1-x)S thin films (x=0 to 1 in steps of 0.1). The variations of conductivity and current-voltage characteristics of these films were investigated as a function of the temperature and applied voltage. The activation energy of the films was found to vary from 0.35 eV to 0.78 eV. © 2011 American Institute of Physics.Item Study of photo-conductivity in nano-crystalline cadmium telluride thin films(2011) Mahesha, M.G.; Bangera, K.V.; Shivakumar, G.K.Nano crystallite thin films of Cadmium Telluride have been grown on glass substrates by thermal evaporation under vacuum. The growth conditions to get stoichiometric films of the compound have been optimized. The effect of substrate temperature and annealing on photosensitivity has been investigated. Also the effect of deposition parameters and post deposition annealing on rise time and decay time have been studied in detail. © 2011 American Institute of Physics.Item Conduction mechanisms in vacuum deposited p-ZnTe/n-Si heterojunction diodes(2011) Rao, G.K.; Bangera, K.V.; Shivakumar, G.K.p-ZnTe/n-Si heterojunction diodes were prepared by vacuum depositing ZnTe films on n-Si substrates. Detailed electrical characterization was performed to determine the conduction mechanisms operating in the diode. Important parameters such as ideality factor and barrier height were also determined. © 2011 American Institute of Physics.Item Fabrication and electrical characterization of vacuum deposited n-CdTe/p-ZnTe heterojunction diodes(2011) Bangera, K.V.; Rao, G.K.; Shivakumar, G.K.The study of n-CdTe/p-ZnTe heterojunctions is of vital importance for the fabrication of single junction and tandem solar cells. In the present research work n-CdTe/p-ZnTe heterojunction diodes were prepared by high vacuum deposition technique. The growth conditions required for obtaining desired quality n-CdTe and p-ZnTe films were optimized by performing a series of trials. The n-CdTe/p-ZnTe heterojunctions were prepared by first depositing CdTe film on glass substrate and then depositing ZnTe flim on top of CdTe. Detailed electrical characterization of the heterojunction was performed. The conduction in the heterojunction was predominantly due to thermionic emission at low voltages. However at higher voltages space charge limited conduction was found to be dominant. The barrier height of the heterojunction was deduced by studying the I-V characteristics. © 2011 American Institute of Physics.Item Conductive and transparent undoped ZnO thin films prepared by thermal evaporation method(2012) Palimar, S.; Shivakumar, G.K.; Bangera, K.V.Zinc Oxide thin films were obtained by thermal evaporation method. The films were then subjected to detailed structural, optical and electrical studies. The analysis has showed that the obtained films have a transmittance of up to 95% in the visible region of the electromagnetic spectrum with a room temperature conductivity of around 92 Ω-1cm-1. A detailed analysis of the result is reported. © 2012 American Institute of Physics.Item X-ray diffraction studies of CdxZn1-xS thin films prepared by spray pyrolysis technique(2013) Raviprakash, Y.; Bangera, K.V.; Shivakumar, G.K.Thin films of CdxZn(1-x)S (0 ≤ x ≤ 1) were deposited on glass substrates by the chemical spray pyrolysis technique using a less used combination of chemicals. The variation of structural properties of these films in relation with composition was studied in detail. The entire study was made for a wide range of compositions of CdxZn (1-x) S thin films (x=0 to 1 in steps of 0.1). XRD studies reveal that all the films are polycrystalline with hexagonal (wurtzite) structure of which reflection peaks associated with (100), (002) and (110) planes were clearly identified for all the films and inclusion of cadmium into the structure of ZnS improved the crystallinity of the films. The value of lattice constants 'a' and 'c' was found to vary with composition from 0.382 to 0.415 nm and 0.625 to 0.675 nm respectively. © (2013) Trans Tech Publications, Switzerland.Item Effect of annealing on the properties of Sb doped ZnO thin films prepared by spray pyrolysis technique(American Institute of Physics Inc. subs@aip.org, 2014) Kumar, N.S.; Bangera, K.V.; Shivakumar, G.K.Sb doped ZnO thin films have been deposited on glass substrate at 450°C using spray pyrolysis technique. The X-ray diffraction studies revealed that the as deposited films are polycrystalline in nature with (100) preferred orientation. Whereas the films annealed at 450° C for 6h show a preferential orientation along (101) direction. Crystallites size varies from 15.7 nm to 34.95 nm with annealing duration. The Scanning electron microscopic analysis shows the plane and smooth surface of the films. The optical properties of annealed films have shown a variation in the band gap between 3.37 eV and 3.19 eV. Transparency of as grown and annealed films decreases from 78 % to 65% respectively in the visible region. The electrical conductivity of the as grown film shows an increase in the electrical conductivity by one order of magnitude with increase in the annealing duration. © 2014 AIP Publishing LLC.Item 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.Item Preparation of vacuum deposited cadmium selenide thin films for optoelectronic applications(Elsevier Ltd, 2016) Santhosh, T.C.M.; Bangera, K.V.; Shivakumar, G.K.Cadmium selenide is a direct band gap material which finds applications in optoelectronic devices. Preparation of the compound semiconductor in thin film form with stable electrical characterization has been investigated in the present study. As deposited films at room temperature (25°C) are non-stoichiometric with excess cadmium and films grown at 180°C substrate temperature are stoichiometric and homogeneous. The crystallinity increases with increase in substrate temperature. The optical band gap determined from absorption measurements lie in the range 1.89 eV - 2.02 eV. Electrical conductivity measurements made in a temperature range from 25°C to 200°C yield thermal activation energy of 0.52eV for stoichiometric films. Films deposited at 180° C and annealed at 200° C for two hours are found to be stabilized in its electrical and structural properties. © 2016 Elsevier Ltd.Item 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).