• V Ganesan

      Articles written in Bulletin of Materials Science

    • Structural morphology of amorphous conducting carbon film

      P N Vishwakarma V Prasad S V Subramanyam V Ganesan

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      Amorphous conducting carbon films deposited over quartz substrates were analysed using X-ray diffraction and AFM technique. X-ray diffraction data reveal disorder and roughness in the plane of graphene sheet as compared to that of graphite. This roughness increases with decrease in preparation temperature. The AFM data shows surface roughness of carbon films depending on preparation temperatures. The surface roughness increases with decrease in preparation temperature. Also some nucleating islands were seen on the samples prepared at 900°C, which are not present on the films prepared at 700°C. Detailed analysis of these islands reveals distorted graphitic lattice arrangement. So we believe these islands to be nucleating graphitic. Power spectrum density (PSD) analysis of the carbon surface indicates a transition from the nonlinear growth mode to linear surface-diffusion dominated growth mode resulting in a relatively smoother surface as one moves from low preparation temperature to high preparation temperature. The amorphous carbon films deposited over a rough quartz substrate reveal nucleating diamond like structures. The density of these nucleating diamond like structures was found to be independent of substrate temperature (700–900°C).

    • Synthesis and characterization of sodium alkoxides

      K Chandran R Nithya K Sankaran A Gopalan V Ganesan

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      Alcohol route is being adopted for cleaning sodium from sodium-wetted small components of coolant circuits of fast reactors. For better understanding of sodium–alcohol reactions and their energetics, the data on thermo-chemical properties such as heats of sodium–alcohol reactions, heats of dissolution, heat capacities, thermal decomposition behaviour, etc of their end products are essential. In order to generate such data, high purity sodium alkoxides, viz. sodium methoxide, sodium ethoxide and sodium 𝑛-propoxide, were prepared by reacting sodium metal with respective alcohol. These compounds were characterized using X-ray diffraction technique and IR spectroscopy. The elemental analysis was carried out by CHNS analyser and atomic emission spectroscopy. Normal chain sodium alkoxides were found to exhibit tetragonal crystal structure. Crystal structures of sodium ethoxide and sodium 𝑛-propoxide are reported for the first time. The IR spectrum of sodium 𝑛-propoxide is also reported for the first time.

    • Effect of annealing on magnetic properties and silicide formation at Co/Si interface

      Shivani Agarwal V Ganesan A K Tyagi I P Jain

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      The interaction of Co (30 nm) thin films on Si (100) substrate in UHV using solid state mixing technique has been studied. Cobalt was deposited on silicon substrate using electron beam evaporation at a vacuum of 4 × 10-8 Torr having a deposition rate of about 0.1 Å/s. Reactivity at Co/Si interface is important for the understanding of silicide formation in thin film system. In the present paper, cobalt silicide films were characterized by atomic force microscopy (AFM) and secondary ion mass spectroscopy (SIMS) in terms of the surface and interface morphologies and depth profile, respectively. The roughness of the samples was found to increase up to temperature, 300°C and then decreased with further rise in temperature, which was due to the formation of crystalline CoSi2 phase. The effect of mixing on magnetic properties such as coercivity, remanence etc at interface has been studied using magneto optic Kerr effect (MOKE) techniques at different temperatures. The value of coercivity of pristine sample and 300°C annealed sample was found to be 66 Oe and 40 Oe, respectively, while at high temperature i.e. 748°C, the hysteresis disappears which indicates the formation of CoSi2 compound.

    • Structural, optical and electrical properties of chemically deposited copper selenide films

      R H Bari V Ganesan S Potadar L A Patil

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      Stoichiometric and nonstoichiometric thin films of copper selenide have been prepared by chemical bath deposition technique at temperature below 60°C on glass substrate. The effect of nonstoichiometry on the optical, electrical and structural properties of the film was studied. The bandgap energy was observed to increase with the increase in at % of copper in composition. The grain size was also observed to increase with the decrease of at % of copper in composition. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), absorption spectroscopy, and AFM. The results are discussed and interpreted.

    • Effect of indium doping on zinc oxide films prepared by chemical spray pyrolysis technique

      Girjesh Singh S B Shrivastava Deepti Jain Swati Pandya T Shripathi V Ganesan

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      We report the conducting and transparent In doped ZnO films fabricated by a homemade chemical spray pyrolysis system (CSPT). The effect of In concentration on the structural, morphological, electrical and optical properties have been studied. These films are found to show (0 0 2) preferential growth at low indium concentrations. An increase in In concentration causes a decrease in crystalline quality of films as confirmed by X-ray diffraction technique which leads to the introduction of defects in ZnO. Indium doping also significantly increased the electron concentrations, making the films heavily 𝑛 type. However, the crystallinity and surface roughness of the films decreases with increase in indium doping content likely as a result of the formation of smaller grain size, which is clearly displayed in AFM images. Typical optical transmittance values in the order of (80%) were obtained for all films. The lowest resistivity value of 0.045 𝛺-m was obtained for film with 5% indium doping.

    • Electronic transport and magnetoresistivity of La0.4Bi0.1Ca0.5–𝑥Sr𝑥MnO3 (𝑥 = 0.1 and 0.2)

      P Subhashini B Munirathinam M Krishnaiah R Venkatesh D Venkateshwarlu V Ganesan

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      Electrical resistivity and magnetoresistive behaviour of bismuth-substituted lanthanum manganites La0.4Bi0.1Ca0.5–𝑥Sr𝑥MnO3 (𝑥 = 0.1 and 0.2) were systematically studied by varying the temperature from 2 to 300 K and the magnetic field up to 12 T. The samples were found to crystallize in rhombohedral structure and their morphology shows near-spherical nanosize crystallites. Charge ordering was observed in both the samples under zero field conditions and corresponding transition temperature 𝑇CO was found to decrease with the increase of 𝑥. Resistivity measurements with magnetic field also showed suppression of magnetoresistivity (MR) with the increase of 𝑥 and the maximum MR was found to be 98 and 93% for 𝑥 = 0.1 and 0.2, respectively, at 10 T. In the high-temperature domain, the electronic transport was observed to be dominated by the variable range hopping mechanism for both the samples, whereas in the low-temperature domain the electrical conduction of 𝑥 = 0.1 sample was observed to be contributed by various other electron scattering mechanisms.

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