Faculty Publications
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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 The measurement of electrical conductivity for the investigation of the number of water molecules present in the mixed crystals of barium copper oxalate and barium ammonium oxalate lattice have been carried out in the temperature range 30 to 450 °C. The dehydration temperature and the number of water molecules removed out of the structure at a particular temperature is estimated from the sharp increase in conductivity at these points. The almost steep increase of conductivity is attributed to the increase in the number of mobile charge carriers H+ and OH– ions generated from the escaping water molecules. The study of electrical conductivity in association with the thermal behaviour has been used to understand the mechanism of conduction. Copyright © 1995 WILEY?VCH Verlag GmbH & Co. KGaA(Electrical Conductivity and Thermal Dehydration Studies of Mixed Single Crystals of BaCu(C2O4)2 · 6 H2O, Ba1–xCuxC2O4 · 4 H2O and Ba1–2x(NH4)2xC2O4 · 4 H2O) Kasthuri, V.B.; Mohan Rao, P.1995Item The effect of substrate temperature on the structural, optical and electrical properties of vacuum deposited ZnTe thin films(2009) Rao, G.K.; Bangera, K.V.; Shivakumar, G.K.The present paper reports the effect of substrate temperature on the structural, optical and electrical properties of vacuum deposited zinc telluride (ZnTe) thin films. X-ray diffraction (XRD) analysis of the films, deposited on glass substrates, revealed that they have cubic structure with strong (111) texture. Room temperature deposits are tellurium rich and an increase in the substrate temperature up to 553 °K results in stoichiometric films. Electrical conductivity has been observed to increase with the increase in substrate temperature, accompanied by increase in the carrier concentration and the mobility of the carriers. The optical bandgap energy and the thermal activation energy of the films have also been evaluated. © 2009 Elsevier Ltd. All rights reserved.Item A comprehensive assessment of increased iron ore production on the environment - A case study(2011) Thimmaiah, S.A.; Rao, Y.; Murthy, C.H.S.N.There has been a significant increase in iron ore production in the Bellary- Hospet-Sandur sector of Karnataka, India due to sudden increase in the demand of iron ore from other countries as well as by local steel plants set up in the region. An attempt has been made in this paper to study the effect of increase in the iron ore production on various environmental parameters like air, water, soil and noise. For this purpose a study area of 10 Km radius was taken and the various environmental parameters were monitored before and after increase in iron ore production in the region. Study shows that there is no significant change in the air quality in terms of SPM, RPM, SO2 and NOx in the region. In many locations, there is decrease in the concentrations of these parameters. This is mainly due to improvement of roads by asphalting, effective covering of iron ore trucks by tarpaulin, awareness among mine owners about the protection of environment by following various pollution control measures, dust suppression measures on the public road using water sprinklers and stringent monitoring of the environmental protective measures by various regulatory authorities. The concentration of SO2 and NOx was found to increase due to increase in traffic by movement of tippers in the public/village road. The deployment of heavy earth moving machinery at mine site also contributed for increase of SO2 and NOx. The surface water quality parameters were found to be within the acceptable limits in the study area. There is no possibility of disturbing/altering ground water table due to mining operations as the mining is being carried out on hill top which is above the general ground level. In agricultural soil, except that of potassium and electrical conductivity, variations in other parameters are insignificant as the agricultural lands are located 2 to 3 Kms away from the active mining area. Increase in noise level is found at most of the locations of the study area. Therefore, serious attempts should be made by mine owners as well as statutory bodies to reduce the sound level at various locations for increasing the quality of life in these locations in terms of sound level. © 2011 CAFET-INNOVA technical society. All right reserved.Item Study of the aluminium oxide doped zinc oxide thin films prepared by thermal evaporation technique(2012) Palimar, S.; Banger, K.V.; Shivakumar, G.K.The present study reports the observations made on investigations carried out to study structural, optical and electrical properties of aluminium oxide doped ZnO thin films obtained by thermal evaporation technique. Films obtained are found to be amorphous in nature with smooth and continuous surface. Room temperature conductivity of the film is found to be 5x10 3 U -1 cm -1 with visible region transmittance of above 95%. The optical energy gap of the film is found to be 3.25 eV. From the calculations of activation energy, it is observed that the doped ZnO film has two donor levels, one at 142 meV and other at 43 meV. A detailed analysis of the result is reported. © 2012 Asian Network for Scientific Information.Item Quantifying aquifer properties and freshwater resource in coastal barriers: A hydrogeophysical approach applied at Sasihithlu (Karnataka state, India)(2012) Vouillamoz, J.-M.; Hoareau, J.; Grammare, M.; Caron, D.; Nandagiri, L.; Legchenko, A.Many human communities living in coastal areas in Africa and Asia rely on thin freshwater lenses for their domestic supply. Population growth together with change in rainfall patterns and sea level will probably impact these vulnerable groundwater resources. Spatial knowledge of the aquifer properties and creation of a groundwater model are required for achieving a sustainable management of the resource. This paper presents a ready-to-use methodology for estimating the key aquifer properties and the freshwater resource based on the joint use of two non-invasive geophysical tools together with common hydrological measurements.
We applied the proposed methodology in an unconfined aquifer of a coastal sandy barrier in South-Western India. We jointly used magnetic resonance and transient electromagnetic soundings and we monitored rainfall, groundwater level and groundwater electrical conductivity. The combined interpretation of geophysical and hydrological results allowed estimating the aquifer properties and mapping the freshwater lens. Depending on the location and season, we estimate the freshwater reserve to range between 400 and 700 L m??'2 of surface area (A± 50%). We also estimate the recharge using time lapse geophysical measurements with hydrological monitoring. After a rainy event close to 100% of the rain is reaching the water table, but the net recharge at the end of the monsoon is less than 10% of the rain. Thus, we conclude that a change in rainfall patterns will probably not impact the groundwater resource since most of the rain water recharging the aquifer is flowing towards the sea and the river. However, a change in sea level will impact both the groundwater reserve and net recharge. © Author(s) 2012.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 Sn doping on structural, optical, electrical and wettability properties of oriented ZnO nanorod arrays(2013) Santhosh Kumar, A.; Nagaraja, K.K.; Nagaraja, H.S.Herein we present a modified sol gel route for the one step fabrication of oriented ZnO nanorod arrays. The method is seed layer free, and nanorods directly attach to a substrate. We also present the effect of tin (Sn) content on the crystallinity, microstructural, optical and electrical properties of the ZnO nanorod arrays. Thermo gravimetric (TG) curves of gel precursors showed that most of the organic groups and other volatiles were removed at about 450 C. X-ray diffraction patterns confirmed that the films were polycrystalline in nature with (002) preferred orientation. The texture coefficient, grain size, dislocation density and lattice parameters of the ZnO arrays were determined. The SEM micrographs revealed that the undoped and 1 at.%Sn doped films were composed of nanorods and the concentration of 2 at.%Sn doping hindered the rod like structure growth and modulated into granular nature. UV-visible transmission spectroscopy indicated that the transparency of the films increased with Sn content. On Sn doping, the films also exhibited a red shift and slight shrinkage of band gap. The electrical studies revealed that 1 at.% of Sn doping enhanced electrical conduction in ZnO films and beyond that the distortion caused in the lattice reduced the conductivity. The contact angle of the ZnO nanostructures varied between 91 and 115 depending upon the Sn content. Therefore, 1 at.%Sn doping into ZnO nanorods improves the crystallinity, electrical conductivity and water contact angle. © 2013 Springer Science+Business Media New York.Item Comparison of structural health assessment capabilities in epoxy - Carbon black and epoxy - Carbon nanotube nanocomposites(2014) Inam, F.; Badekai Ramachandra, B.; Luhyna, N.; Vo, T.A novel method for comparing structural health of different types of brittle epoxy nanocomposites filled with carbon nanostructured fillers is presented. Epoxy - 0.2 vol% carbon black (CB) and epoxy - 0.2 vol% carbon nanotube (CNT) nanocomposite bars were prepared by calendering and thermal curing. Nanocomposite bars were subjected to Vickers diamond indentation to produce sub-surface damage. Electrical conductivities were analysed by 4-point method to estimate the structural damage caused by indentation. For comprehensive comparison, fracture toughness and percolation threshold were analysed as well. Because of the systematically induced indentation damage, a sharp decrease of 89% was observed in the electrical conductivity of epoxy - CNT nanocomposite as compared to 25% in the electrical conductivity of epoxy - CB nanocomposite. CNTs impart superior damage sensing capability in brittle nanocomposite structures, in comparison to CB, due to their high aspect ratio (fibrous nature) and high electrical conductivity. © BME-PT.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.