Faculty Publications
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Item Properties of ZnO:Bi thin films prepared by spray pyrolysis technique(Elsevier Ltd, 2013) Sadananda Kumar, N.; Bangera, K.V.; Anandan, C.; Shivakumar, G.K.Undoped and Bi doped zinc oxide thin films were deposited on glass substrate at 450 °C using spray pyrolysis technique. The X-ray diffraction studies shows that Bi doped ZnO films are polycrystalline hexagonal structure with a preferred orientation along (101) direction. Crystallites size of the films decreases with increasing doping concentration. Scanning electron microscope image shows change in the surface morphology. The composition of Zn, O and Bi elements in the undoped and Bi doped ZnO films were investigated by X-ray photoelectron spectroscopy. Bi doped ZnO thin films show a transparency nearly 75% in the visible region. The optical band gap of ZnO thin films reduces from 3.25 eV to 3.12 eV with an increase in Bi concentration from 0 to 5at.% respectively. Electrical conductivity of ZnO thin films increased from 0.156 to 6.02S/cm with increasing Bi dopant concentration from 0% to 5% respectively. © 2013 Elsevier B.V. All rights reserved.Item Effect of annealing on the properties of Bi doped ZnO thin films grown by spray pyrolysis technique(Academic Press, 2014) Sadananda Kumar, N.; Bangera, K.V.; Shivakumar, G.K.The effect of annealing temperature on the structural, optical and electrical properties of transparent and conducting Bi doped ZnO (BZO) films deposited on glass substrate by spray pyrolysis technique was investigated. The BZO thin films were annealed in the temperature range from 450 °C to 550°C for 4 h in air atmosphere. The grain size of the BZO films increased with increasing annealing temperature. The annealed BZO films were electrically stable and there was a drastic change in the electrical conductivity after annealing. The films annealed at 500°C showed better conductivity and optical transmittance. © 2014 Elsevier Ltd. All rights reserved.Item Effect of annealing on the properties of zinc oxide nanofiber thin films grown by spray pyrolysis technique(Springer Nature, 2014) Sadananda Kumar, N.; Bangera, K.V.; Shivakumar, G.K.Zinc oxide nanofiber thin films have been deposited on glass substrate by spray pyrolysis technique. The X-ray diffraction studies revealed that the films are polycrystalline with the hexagonal structure and a preferred orientation along (002) direction for films annealed for 1 h at 450 °C. Further increase in annealing time changes the preferred orientation to (100) direction. The scanning electron microscopic analysis showed the formation of ZnO nanofiber with an average diameter of approximately 800 nm for annealed films. The compositional analysis of nanofiber ZnO thin films were studied by time of flight secondary ion mass spectroscopy, which indicated oxygen deficiency in the films. The optical properties of annealed films have shown a variation in the band gap between 3.29 and 3.20 eV. The electrical conductivity of the as grown and annealed films showed an increase in the conductivity by two orders of magnitude with increase in annealing duration. © 2013, The Author(s).Item Properties of CdxZn1-xO thin films and their enhanced gas sensing performance(Elsevier Ltd, 2017) Bharath, S.P.; Bangera, K.V.; Shivakumar, G.K.CdxZn1-xO(0 ? x ? 0.20) thin films with different Cd concentrations were successfully deposited on glass substrate using spray pyrolysis technique. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX) were used for structural, surface morphological and compositional characterization. The XRD analysis revealed that the synthesized films were hexagonal in structure with (002) orientation. The SEM studies confirm the formation of homogeneous and uniform films. Optical transmittance and electrical conductivity of the films were evaluated using UV–Visible spectroscopy and two probe method respectively. The optical studies showed that the CdxZn1-xO thin films have optical transmittance in entire visible region. The resistivity of undoped films were very high and it decreases with addition of cadmium. The gas sensing properties were investigated at optimal temperature of 350 °C for various volatile organic compounds like acetone, ethanol and methanol. The CdxZn1-xO thin films with 10 at. % cadmium concentration showed the sensitivity of 50% for 1 ppm ethanol. © 2017 Elsevier B.V.Item 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.Item 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. © 2017Item 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 GmbHItem Effect of cadmium incorporation on the properties of zinc oxide thin films(Springer Nature, 2018) Bharath, S.P.; Bangera, K.V.; Shivakumar, G.K.CdxZn1-xO (0 ? x ? 0.20) thin films are deposited on soda lime glass substrates using spray pyrolysis technique. To check the thermal stability, CdxZn1-xO thin films are subjected to annealing. Both the as-deposited and annealed CdxZn1-xO thin films are characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray analysis (EDAX) to check the structural, surface morphological and compositional properties, respectively. XRD analysis reveals that the both as-deposited and annealed CdxZn1-xO thin films are (002) oriented with wurtzite structure. SEM studies confirm that as-deposited, as well as annealed CdxZn1-xO thin films are free from pinholes and cracks. Compositional analysis shows the deficiency in Cd content after annealing. Optical properties evaluated from UV-Vis spectroscopy shows red shift in the band gap for CdxZn1-xO thin films. Electrical property measured using two probe method shows a decrease in the resistance after Cd incorporation. The results indicate that cadmium can be successfully incorporated in zinc oxide thin films to achieve structural changes in the properties of films. © Springer-Verlag GmbH Germany, part of Springer Nature 2018.Item Effect of indium content on the characteristics of indium tin oxide thin films(Institute of Physics Publishing helen.craven@iop.org, 2018) Navya, K.; Bharath, S.P.; Bangera, K.V.; Shivakumar, G.K.Transparent IxT1-xO (x = 0 to 1) alloyed thin films were deposited by spray pyrolysis technique at a substrate temperature of 400 °C. The effect of incorporation of indium on structural, optical and electrical properties of tin oxide thin films were studied. Characterization of thin films was carried out using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDAX), UV-Visible absorption spectroscopy. XRD results revealed that IxT1-xO thin films were polycrystalline in nature with good crystallinity. Incorporation of indium effectively modifies the surface morphology of the films. The band gap was varied from 3.7 eV to 3 eV. Maximum electrical conductivity of 44.52 × 103 ?-1 m-1 and transmittance of 90% is obtained for I0.5T0.5O films, hence can be used as highly transparent and conducting electrodes. © 2018 IOP Publishing Ltd.Item Synthesis and characterization of Cu 1-x Zn x O composite thin films for sensor application(Elsevier Ltd, 2019) Bharath, S.P.; Bangera, K.V.; Shivakumar, G.K.Cu 1-x Zn x O composite thin films were prepared using industrially applicable spray pyrolysis technique for volatile organic compound (VOCs)sensor application. Sensing properties for different concentration of VOCs such as acetone, ethanol and methanol were studied at different sensor operating temperature. XRD studies on prepared thin films confirmed formation of CuO[sbnd]ZnO composite thin films with presence of different peaks for monoclinic structured CuO and hexagonal structure ZnO, it was also observed that formation of composite material improves sensing property towards VOCs. Granular morphology observed from SEM images were also contributed to enhance sensitivity of Cu 1-x Zn x O thin films. Hot probe experiment reveals that all the thin films were p-type in conductivity nature. Maximum electrical conductivity was achieved for Cu 0.75 Zn 0.25 O composite thin films, which also showed highest sensing property for VOCs. Cu 0.75 Zn 0.25 O thin films were selective towards ethanol and were capable of detecting 1 ppm of ethanol at operating temperature of 290 °C. © 2019