Department of Physics

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    Oxidation mechanism of thin Cu films: A gateway towards the formation of single oxide phase
    (AIP, 2018) Gangopadhyay, Subhashis; Pande, Surojit
    Controlled thermal oxidations of thin copper films at relatively lower temperatures (up to 500°C) leading towards the formation of a single phase of copper oxide are investigated where the oxidation temperature, duration, oxygen partial pressure, film thickness and the crystallographic orientations play very crucial roles to significantly control the final phase of the copper oxide. Thin Cu films of thicknesses 100-1000 nm were deposited on glass and silicon substrates using the vacuum assisted thermal evaporation technique. Oxidations of those Cu films were performed at different temperatures for variable durations in air ambient as well as oxygen ambient conditions. Four probe resistivity measurement, x-ray diffraction (XRD), Raman spectroscopy, ultraviolet–visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM) and x-ray photoemission spectroscopy (XPS) techniques have been used to characterize the oxide films. At a thermodynamic equilibrium, it has been observed that the oxide phase is solely determined by the oxidation temperature, however, the oxygen partial pressure can significantly alter this temperature range. In case of thermal oxidation in air, the initial oxidation of the copper films starts at about 150 °C, but a well ordered crystalline phase of the cuprous oxide (Cu2O) is observed only above 200 °C. However, the cupric oxide (CuO) phase starts to appear only above 320 °C. The details of the oxidation mechanism of the Cu film are explained with a probable schematic model in terms of thermal diffusion as well as the chemical reactivity.
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    Detection of cadmium ion in water using films of nanocomposite of functionalized carbon nanotubes and anionic polymer
    (AIP, 2018-05) Manjuladevi, V.; Gupta, Raj Kumar
    Presence of cadmium in drinking water is one of the major threats to human health. According to international standards, the maximum permission concentration of cadmium ion in drinking water should be less than 0.002 to 0.010mg/l (2-10 ppb). It is one of the major contaminants in potable water in western part of Indian subcontinent. It is found up to 2.3 to 8.6 mg/l in Rajasthan water. In this article, we report our study on detection of cadmium ion in water employing a sensing layer of nanocomposites of functionalized single walled carbon nanotubes (SWCNTs) and polyacrylic acid (PAA). The film was deposited onto 5 MHz AT-cut quartz crystal of a quartz crystal microbalance (QCM). The response was collected in both static and dynamic mode. We obtained a linear response curve in a given concentration range of cadmium ion indicating the suitability of the functional layer for cadmium ion detection in water. The surface morphology of the functional layer was studied using atomic force microscope before and after sensing.
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    Interaction of bovine serum albumin protein with self assembled monolayer of mercaptoundecanoic acid
    (AIP, 2016-05) Manjuladevi, V.; Gupta, Raj Kumar
    Detection of proteins and other biomolecules in liquid phase is the essence for the design of a biosensor. The sensitivity of a sensor can be enhanced by the appropriate functionalization of the sensing area so as to establish the molecular specific interaction. In the present work, we have studied the interaction of bovine serum albumin (BSA) protein with a chemically functionalized surface using a quartz crystal microbalance (QCM). The gold-coated quartz crystals (AT-cut/5 MHz) were functionalized by forming self-assembled monolayer (SAM) of 11-Mercaptoundecanoic acid (MUA). The adsorption characteristics of BSA onto SAM of MUA on quartz crystal are reported. BSA showed the highest affinity for SAM of MUA as compared to pure gold surface. The SAM of MUA provides carboxylated surface which enhances not only the adsorption of the BSA protein but also a very stable BSA-MUA complex in the liquid phase.
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    Synthesis and characterization of novel electronic-ionic glass-ceramic system for cathode applications
    (AIP, 2020-11) Dalvi, Anshuman
    Li+ NASICON based mixed conducting glass-ceramic composites have been developed by mechanical milling assisted synthesis where the mixed ion conducting glass [90V2O5-10P2O5] (abbreviated as VOPO) has been externally dispersed in LiTi2(PO4)3 (LTP). The glass-ceramic with a composition 10(VOPO-0h)-90(LTP-18h) (in wt%) has been structurally and electrically characterized. XRD shows no precipitation of any crystalline phase from VOPO in resultant glass-ceramic composite. The highest total conductivity has been found to be ∼10−5 Ω−1cm−1 at 100 °C which is relatively higher than that of LTP. The total electrical transport is found to be due to the conduction of electrons and Li+ ions in the composite. Reversible cyclic voltammetry scans suggest ohmic nature of the composites. These materials have been found to be suitable as cathodes for Li+ ion battery applications.