Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
9 results
Search Results
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 Study of the doping of thermally evaporated zinc oxide thin films with indium and indium oxide(Springer Nature, 2013) Palimar, S.; Bangera, K.V.; Shivakumar, G.K.The present paper reports observations made on investigations carried out to study structural, optical and electrical properties of thermally evaporated ZnO thin films and their modulations on doping with metallic indium and indium oxide separately. ZnO thin film in the undoped state is found to have a very good conductivity of 90 ?–1 cm–1 with an excellent transmittance of up to 90 % in the visible region. After doping with metallic indium, the conductivity of the film is found to be 580 ?–1 cm–1, whereas the conductivity of indium oxide-doped films is increased up to 3.5 × 103 ?–1 cm–1. Further, the optical band gap of the ZnO thin film is widened from 3.26 to 3.3 eV when doped with indium oxide and with metallic indium it decreases to 3.2 eV. There is no considerable change in the transmittance of the films after doping. All undoped and doped films were amorphous in nature with smooth and flat surface without significant modifications due to doping. © 2012, The Author(s).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 Bi doping on the properties of CdSe thin films for optoelectronic device applications(Elsevier Ltd, 2017) Santhosh, T.C.M.; Bangera, K.V.; G.k, S.CdSe and Bi (1%, 2%, 3%) doped CdSe thin films were deposited on the glass substrates using thermal evaporation technique. Effect of Bi doping on the structural, optical, electrical and photo response properties of CdSe thin films were investigated. The X-ray diffraction studies reveals that undoped and Bi doped CdSe films are polycrystalline in nature with hexagonal crystal structure along (002) direction. No significant changes are observed in the lattice parameters or the grain size indicating minimum lattice distortion. The optical band gap of undoped CdSe film was estimated to be 1.67 eV. Replacement of cadmium by bismuth results in an increase in the electrical conductivity of doped films. Doping with bismuth is found to improve the photo sensitivity of CdSe thin films. © 2017 Elsevier LtdItem Enhanced gas sensing properties of indium doped ZnO thin films(Academic Press, 2018) Bharath, S.P.; Bangera, K.V.; Shivakumar, G.K.Indium doped ZnO (InxZn1-xO, 0 ? x ? 0.05) thin films were deposited on to soda lime glass substrate by employing spray pyrolysis as deposition technique. Effect of doping concentration on characteristics of thin films were examined by XRD, SEM, UV-Visible spectroscopy, electrical and gas sensing measurements. XRD analysis demonstrates polycrystalline nature of thin films and also shows the shift in orientation from (002) to (101) crystal plane with increase in indium doping concentration. Surface morphological analysis shows the formation of homogeneous particle like nanostructures. Optical transmittance determined from UV-Visible spectroscopy was in the range of 80–95%, which was decreasing with increase in indium doping concentration. Maximum electrical conductivity was achieved at an optimal indium doping concentration of 3 at.%. The gas sensing properties were examined for different concentration of volatile organic compounds like acetone, ethanol and methanol for different doping levels. In0.03Zn0.97O thin films showed good sensitivity towards ethanol, with sensitivity of 30% towards 25 ppm of ethanol. © 2018 Elsevier LtdItem Preparation of thermally deposited Cux(ZnS)1-x thin films for opto-electronic devices(Elsevier Ltd, 2019) Barman, B.; Bangera, K.V.; Shivakumar, G.K.Zinc sulfide thin films have been doped with copper atoms to investigate their efficiency as transparent conductor layers. Cux(ZnS)1-x thin films were deposited on glass substrate using thermal evaporation technique by varying the Cu concentration (x = 0.01, 0.02, 0.03, 0.05, 0.10 and 0.25). The prepared thin films were characterized using XRD, FE-SEM, EDS and UV–Vis spectroscopy. The X-ray diffraction studies revealed that the films are crystalline in nature and well oriented along (111) direction with the cubic crystal structure. Crystallite size increases with increase in Cu concentration. FE-SEM studies showed that the films are homogenous and pin-hole free. All the films exhibited p-type conductivity. It was also observed that the band gap of the Cux(ZnS)1-x films vary from 3.48 eV to 2.60 eV when the copper content varies from 0 to 0.25. At a Cu concentration of x = 0.03, the hole conductivity increases to 1.9 × 103 S/m retaining an optical transparency of ?73% in the visible spectra. This combination of optical transparency and hole conductivity of Cux(ZnS)1-x thin films for such low Cu concentration is, to our knowledge, the best reported to date. © 2018Item Enhanced thermoelectric power of Al and Sb doped In 2 Te 3 thin films(Elsevier Ltd, 2019) Vallem, V.; Bangera, K.V.; G.k, S.Aluminium and antimony are used as dopants for In 2 Te 3 to study their influence on the thermoelectric power of the films. Both aluminium and antimony are expected to replace indium in the film and contribute to the structural, electrical and thermoelectric behaviour of indium telluride. It is observed that addition of both Al and Sb dopants induced an additional phase of free Te. The electrical conductivity of In 2 Te 3 films is observed to reduce with Al doping and increase with Sb doping when compared with the electrical conductivity of un-doped films. The thermoelectric power is found to be maximum for 2.1% Al doped and 1% Sb doped films. Moreover, the thermoelectric power factor of In 2 Te 3 films is found to be enhanced 3.1 times for 2.1% doping of Al and 8.7 times for 1% Sb doping. © 2019 Elsevier LtdItem Drastic increase in thermoelectric power factor of mixed Sb2Te3-In2Te3 thin films(Academic Press, 2019) Vallem, S.; Bangera, K.V.; G.k, S.Thermoelectric power factor is an indicator of the performance of a thermoelectric material. Attempts have been made by various techniques, like doping, to improve the thermoelectric conversion efficiency of materials. In the present study, a layer structured thermoelectric material Sb2Te3 is alloyed to In2Te3 using vacuum deposition method at 423 K to significantly enhance the power factor of ?118 ?Wm-1K?2 (at 450 K). Structurally, all films were polycrystalline in nature as clearly reflected in XRD patterns. All films were showing p-type conductivity, and electrical conductivity of In2Te3 films increased with increasing Sb2Te3 content. The seebeck coefficient is found to be higher for un-doped In2Te3 than that of Sb2Te3-In2Te3 and pure Sb2Te3 films. However, the thermoelectric power factor of 25% Sb2Te3 alloyed In2Te3 films is enhanced by 11.9 times that of In2Te3 films and 4 times that of Sb2Te3 films at 320 K. It is interesting to note that efficiency of the mixed films is higher than that of the individual films. © 2019 Elsevier LtdItem Fast detection and discriminative analysis of volatile organic compounds using Al-doped ZnO thin films(Springer Science and Business Media Deutschland GmbH, 2021) Bharath, S.P.; Bangera, K.V.Abstract: Aluminum-doped zinc oxide (AZO) thin films with different doping concentrations have been synthesized by simple spray pyrolysis technique. Precursor solution concentration was maintained ~ 50 mM throughout the fabrication process and dopant concentration was varied from 0 to 5 at. %. Prepared solution was sprayed on top of pre-heated glass plate to get highly adhesive AZO thin films. Various characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Visible spectroscopy were adopted to get an insight into the material formation. Electrical and gas-sensing characteristics were also recorded in detail to evaluate its potential application as a transparent conductor and gas sensor. As determined from XRD analysis, continuous decrease in grain size was observed with increase in aluminum doping concentration. Further, extracting the interplanar distance and lattice parameters, it was noticed that there was a negligible random variation. Aluminum doping also plays a significant role in modifying the surface morphology of thin films. Randomly arranged plate-like structures in undoped ZnO thin films transform to granular morphology with aluminum doping. Minimum resistivity of 0.517?m with ~ 80% transmittance in visible region was achieved at an optimal aluminum doping concentration of 3 at.%. Aluminum doping helps in increasing the sensitivity of ZnO thin films toward various volatile organic compound vapors such as acetone and ethanol. 3 at.% Al-doped thin films were capable of detecting 100 ppm of ethanol and acetone with a highest sensitivity of ~ 60%. Al incorporation to ZnO lattice is also supportive in bringing down the response and recovery time of the sensing material. A very short response time of 3 s and recovery time of 28 s was achieved at 100 ppm of ethanol. Principal component analysis shows proper discrimination between acetone and ethanol. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.