R. Jayavel

Growth and characterization of zinc thiourea chloride (ZTC): a semiorganic nonlinear optical crystal

Growth of bulk zinc thiourea chloride single crystals from aqueous solution by solution growth technique is reported. It has been found that the solution pH influences the growth rate of the crystal along [0 0 1] and [0 1 0] directions. Single crystal X-ray diffraction analysis confirms the crystal structure. The grown crystals have been subjected to optical and mechanical property studies.

Structural and optical properties of thin zirconium oxide films prepared by reactive direct current magnetron sputtering

Thin films of zirconium oxide have been deposited onto glass and Si(100) substrates at room temperature by reactive dc magnetron sputtering of a metallic Zr target in an argon–oxygen atmosphere. The films were characterized by Rutherford backscattering spectroscopy, x-ray diffraction, x-ray reflectometry, atomic force microscopy, and optical spectroscopy to investigate the variation of stoichiometry, structure, density, and optical properties upon increasing oxygen partial pressure. The Zr target shows a well-defined hysteresis upon varying the oxygen pressure as determined by quartz crystal microbalance measurements. Rutherford backscattering experiments reveal that the films are metallic with a small amount of oxygen incorporation at oxygen flows well below 2.7 sccm. Stoichiometric ZrO2 films, however, are formed above 2.8 sccm O2 flow (oxidic mode). Grazing angle incidence x-ray diffraction studies show that crystalline ZrO2 films with monoclinic structure grow in this oxygen flow regime. X-ray reflect...

Growth of zinc thiourea sulfate (ZTS) single crystals: a potential semiorganic NLO material

The growth of zinc thiourea sulfate (ZTS) single crystals has been investigated. The crystals were grown from aqueous solution by slow cooling technique. The influence of pH on both the morphology and growth rate of ZTS crystals has been studied. The results indicated that the growth rate of the ZTS crystal along the c-direction, R *0 0 1+ was faster than the rate along the a-direction, R *1 0 0+ , if the pH is increased. Powder X-ray di⁄raction and single-crystal X-ray di⁄raction studies confirm the crystal structure and single crystallinity, respectively. The presence of sulfur-to-zinc bonds in the complex has been revealed by Fourier transform infrared analysis. ( 1999 Elsevier Science B.V. All rights reserved.

Growth of bis(thiourea) cadmium chloride single crystals — a potential NLO material of organometallic complex

Growth aspects of bis(thiourea) cadmium chloride (BTCC) single crystals has been investigated. The crystals were grown from aqueous solution by slow cooling technique. The effect of pH on the growth rate and morphology has been discussed. The results indicated that as the pH of the solution is decreased the growth rate along the a-direction, R[100] increased and at a pH below 1, the morphology of the crystals changes from hexagonal to rectangular. Single crystal X-ray diffraction studies confirm the structure. Fourier transform infrared analysis and single crystal X-ray diffraction analysis confirms the presence of sulfur to cadmium bonds in the complex.

Characterization of cadmium doped zinc oxide (Cd : ZnO) thin films prepared by spray pyrolysis method

Thin films of cadmium doped zinc oxide (Cd : ZnO) with different cadmium concentrations have been prepared by the spray pyrolysis method on different substrates at 400 °C. The physical properties of the films were studied as a function of increasing cadmium dopant concentration (up to 25 wt%). The films were characterized by different methods to understand their structural, optical and electrical properties. Energy dispersive x-ray diffraction spectroscopy analysis showed that the Cd concentration in the solid film is slightly lower than that of the starting solution. The x-ray diffraction analysis revealed that the films are polycrystalline in nature having a hexagonal wurtzite type crystal structure with a preferred grain orientation in the (0 0 2) direction. Due to Cd doping, the degrees of polycrystallinity increased simultaneously and the orientation of the grains in the (0 0 2) axis is found to be deteriorated. Atomic force microscopy measurements reveal that the surface morphology of the films changes continuously with a decrease in the grain size due to Cd doping. Both photoluminescence and optical measurements showed that the band gap decreases from 3.12 to 2.96 eV with increasing Cd concentration. Increasing the Cd concentration also leads to the broadening of the emission peak and degrading the crystalline quality. The films are highly transparent in the visible region and the absorption edge showed a red shift. The sheet resistance of pure ZnO has been determined as 650 Ω sq−1 cm−1 and is decreased for higher concentrations of Cd doping. The characterization studies clearly indicate the incorporation of Cd into ZnO; hence the observed decrease in the optical band gap and electrical resistivity can be directly attributed to the effect of Cd ion incorporation into the ZnO lattice.

Metastable zonewidth, induction period and interfacial energy of zinc tris(thiourea) sulfate

Metastable zonewidth and induction period measurements on ZTS and ZTSP crystals are presented. The effect of pH on the solubility, metastable zonewidth and induction period has been studied. The effect of substitution of phosphate on the nucleation parameters has been presented. The interfacial energy for pure and phosphate mixed ZTS solutions at 30°C has also been estimated. There is a significant variation in the induction period and interfacial energy due to decrease in solution pH and phosphate substitution.

Temperature stability of sputtered niobium-oxide films

The effect of annealing temperature on the structural and optical properties of sputtered niobium–oxide films has been investigated. The temperature dependence of structure, density, and optical constants has been studied by Rutherford backscattering, x-ray diffraction, x-ray reflection, optical spectroscopy, and variable angle spectroscopic ellipsometry techniques. Rutherford backscattering measurements show no variation in the stoichiometry of the films upon annealing of amorphous Nb2O5 films, while amorphous NbO is oxidized to Nb2O5. X-ray diffraction studies show that as-deposited films are amorphous and only crystallize at around 500 °C. X-ray reflectivity studies reveal a continuous increase of film density with increasing annealing temperature. Optical spectroscopy and spectroscopic ellipsometry confirm that the refractive index n and the band gap Eg increase upon increasing annealing temperature. The variation of the refractive index with density of the niobium–oxide films is observed to follow th...

Growth and characterisation of phosphate mixed ZTS single crystals

Abstract The growth of zinc tris (thiourea) sulfo-phosphate, ZTSP, single crystals from aqueous solution by a low temperature solution growth technique is reported. ZTSP crystals were grown by partial substitution of sulfate with phosphate. The growth was carried out for different mol.% of phosphate and the incorporation of phosphate in the grown crystals was quantified by ICP analysis. The incorporation of phosphate in the grown crystals was qualitatively analysed from FTIR studies. Morphological changes have been observed for the crystals grown at different mol.% of phosphate. Absorption spectra taken for the pure and phosphate mixed ZTS crystals reveal that the phosphate mixed ZTS crystal may be a better nonlinear optical (NLO) material for second harmonic generation (SHG). The Vicker’s microhardness number was found to increase with phosphate substitution.

Dimensionally integrated nanoarchitectonics for a novel composite from 0D, 1D, and 2D nanomaterials: RGO/CNT/CeO2 ternary nanocomposites with electrochemical performance

We report a one-step conversion of a dimensionally mixed ternary nanocomposite from zero-dimensional (0D) cerium oxide (CeO2), one-dimensional (1D) carbon nanotubes (CNTs), and two-dimensional (2D) reduced graphene oxide (RGO) nanomaterials by the chemical precipitation method. The RGO/CNT/CeO2 ternary nanocomposite showed excellent electrochemical performance (electrical double layer capacitor properties) in an aqueous electrolyte followed by long term cyclic stability and high energy density compared to its binary counterparts.

Enhanced Photocatalytic Performance of the Graphene-V2O5 Nanocomposite in the Degradation of Methylene Blue Dye under Direct Sunlight

A simple and efficient solution mixing method has been developed for the synthesis of the G-V2O5 nanocomposite. By this method, one-dimensional V2O5 rods are decorated onto the two-dimensional graphene sheets. The synthesized nanocomposites are characterized by XRD, SEM with elemental mapping, TEM, FT-IR, Raman, BET, and XPS analyses. The photocatalytic activity of the G-V2O5 nanocomposite studied with methylene blue dye shows strong degradation efficiency with direct sunlight irradiation compared to UV and visible light sources. The mechanism of methylene blue dye degradation by the G-V2O5 nanocomposite has been elucidated through the kinetics of the degradation process by calculating the rate constant and half-life time of the degradation process.