Department of Physics

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Author: search.filters.author.Manjuladevi, V.Subject: search.filters.subject.Thin films

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Now showing 1 - 5 of 5
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    Scanning tunneling spectroscopy of thin films of carbon nanotubes
    (AIP, 2013) Gupta, Raj Kumar; Manjuladevi, V.
    The thin films of single walled carbon nanotubes (CNT) were deposited on indium tin oxide (ITO) glass substrates. The films were characterized using scanning tunneling microscopy and spectroscopy. The topographic images reveal a high degree of orientational order in the arrangement of bundles of CNT onto the ITO substrates. We found a significant narrowing of the band gap of the CNT films on ITO as compared to that of ITO film on glass substrate.
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    Formation of H-type liquid crystal dimer at air-water interface
    (AIP, 2014) Manjuladevi, V.; Gupta, Raj Kumar
    We have formed the Langmuir monolayer of H-shaped Azo linked liquid crystal dimer molecule at the air-water interface. Isocycles of the molecule showed hysteresis suggesting the ir-reversible nature of the monolayer formed. The thin film deposited on the silicon wafer was characterized using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The images showed uniform domains of the dimer molecule. We propose that these molecules tend to take book shelf configuration in the liquid phase.
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    Sensing of contaminants in potable water using TiO{sub 2} functional film
    (AIP, 2016) Manjuladevi, V.
    The piezoelectric based quartz crystal microbalance is employed for sensing contaminants in potable water. A spin coated thin layer of TiO{sub 2} nanoparticles was formed at the sensing area of a 5 MHz AT-cut quartz wafer. The thin film of TiO{sub 2} nanoparticles forms a mesoporous functional layer for the trapping of water borne contaminants. The morphology of the thin film of TiO{sub 2} nanoparticles was studied using field emission scanning electron microscope (FESEM). The surface morphology of the TiO{sub 2} nanoparticles reveals the mesoporous structures indicating large number of defects and porous sites. Such film was employed for the detection of water borne contaminants by detecting the piezoelectric response from a quartz crystal microbalance. We found the film to be very sensitive to the contaminants. The minimum detection limit was found to be 330 ppb. The effect of surface recharging was also studied by altering the physical conditions so that the film can be used for repetitive usage.
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    Sensing of contaminants in potable water using TiO2 functional film
    (AIP, 2016-04) Manjuladevi, V.; Gupta, Rajiv; Gupta, Raj Kumar
    The piezoelectric based quartz crystal microbalance is employed for sensing contaminants in potable water. A spin coated thin layer of TiO2 nanoparticles was formed at the sensing area of a 5 MHz AT-cut quartz wafer. The thin film of TiO2 nanoparticles forms a mesoporous functional layer for the trapping of water borne contaminants. The morphology of the thin film of TiO2 nanoparticles was studied using field emission scanning electron microscope (FESEM). The surface morphology of the TiO2 nanoparticles reveals the mesoporous structures indicating large number of defects and porous sites. Such film was employed for the detection of water borne contaminants by detecting the piezoelectric response from a quartz crystal microbalance. We found the film to be very sensitive to the contaminants. The minimum detection limit was found to be 330 ppb. The effect of surface recharging was also studied by altering the physical conditions so that the film can be used for repetitive usage.
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    Synthesis, phase to phase deposition and characterization of rutile nanocrystalline titanium dioxide (TiO2) thin films
    (Elsevier, 2013-01) Gupta, Raj Kumar; Manjuladevi, V.
    In this work the preparation, deposition and structural properties of titanium oxide (TiO2) thin films were investigated. The films were deposited by means of the e-beam physical vapor deposition (EBPVD) method in high vacuum (10−7 Torr). A controlled deposition rate in the range of 0.1–0.3 Å/s was monitored in situ employing quartz crystal. The films were deposited on the oxidized Si (1 0 0) wafer, glass micro slides. These films were analyzed using Grazing Angle X-ray diffraction (GA-XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy (RAMAN), Atomic Force Microscopy (AFM) and UV–visible Spectroscopy (UV–vis). Structural characterization results showed mainly presence of the crystalline rutile phase, however an interfacial SiO2 layer between TiO2 and the substrate and the minor anatase crystalline phase of TiO2 was also identified in FTIR analysis. Grain size was found to be in the range of 100–125 nm while grain boundary was estimated to be 20 nm. Direct and indirect optical band gap was estimated to be 3.64 and 3.04 eV, respectively. A process induced self annealing of deposited film shows a strong effect on the structural, morphological and optical properties. Furthermore, low deposition rate and high vacuum allows rutile to rutile phase transformation from indigenously prepared TiO2 target to thin film.