Papers by Keyword: Raman Spectrum

Abstract: Coumarin dye laser compounds are often used as components in coloring agents and sprays., as well as in the odorization of foods. Therefore, the important of these compounds in many felids leading to growth of several ways aiming to advance the control of pharmaceutical and superficial producing. Solvents play an important role in changing the character of coumarin. The investigated spectral properties, as well as the effect of changing the solvent on this property, have been published. results referred that the molar electronic transition energy increased with decreasing the maximum absorption wavelength, and the highest intensity of the absorption spectrum was in the case of acetone solvent. In addition, many bands appear in Raman shift attributed to the ''C=O'' band, ''O=C–O, C–C'', and ''C–O'' deformation. The characteristic vibrations involving the ''O-H'' group is the stretching and bending modes of the ''O-H'' and ''C-O'' parts.

Abstract: This research took CH₄ and H₂ as the air source and sufficiently utilized the diamond films generated on the Si piece due to the microwave plasma chemical vapor deposition (MPCVD) method. Raman spectrum functioned as the key method to investigate the diamond films in such research. The diamond phase, large graphite monocrystals and the disorderly graphite in the films were related respectively to different Raman characteristic peaks. An analysis and related investigation on the Raman spectrum of the sample revealed the performance parameters of the structure, purity and stress of the diamond films in different concentrations of the air source.

Abstract: A lanthanum doped lead zirconate titanate (PLZT) ceramic specimen was prepared by the conventional solid state reaction method. The crystal phase and morphology of the PLZT specimen were characterized by XRD and SEM techniques, with the hysteresis loop by RT6000HVS system. The compressive stress was applied to the PLZT specimen through the microtest mechanical loading device. In-situ Raman spectra focused on a fixed grain under various compressive stresses were recorded for different polarization directions of the scattered light. The effects of stresses on the Raman spectra and the intensity ratio between the E+B1 and E(2TO) modes are discussed.

Abstract: In this paper, we study the ground-state and lattice dynamical properties of β-UH--₃ by means of the first-principles density functional theory within the local spin-density approximation (LSDA)+U formulism. The lattice constants and electronic structure are correctly described by taking into account the strong on-site Coulomb repulsion among the 5f electrons localized on uranium atoms. Good agreement with experiments is achieved by tuning the effective Hubbard parameter at around 4 eV. The phonon band structure confirms the dynamical stability of β-UH--₃, and the Raman-active modes are consistent with Raman spectrum measurements. The substitution of the deuterium (tritium) atom for hydrogen atom makes significant variations in the typical frequency of Raman-active modes. It is found that the Raman-active mode frequency is approximately inversely proportional to the square root of the hydrogen isotope mass. We conclude that Raman spectrum provides a powerful method for detecting hydrogen isotopic effects.

Abstract: In this paper, from the standpoint of Raman spectrum research aspect in material science, Raman spectrum analysis of graphite and diamond microcrystal retained by gallium phosphide nanoparticles is introduced. We found that molecular configuration of basic fuchsin adsorbed on gallium phosphide nanoparticles through experiments. Based on these, Raman scattering is used for analyzing basic fuchsin adsorbed on surface of gallium phosphide nanoparticles. Moreover, we discuss the corresponding meanings of agglomeration phenomenon from the perspective of material.

Abstract: Diamond films were deposited by using methane and hydrogen as the gas source and utilizing the approach of chemical vapor deposition of microwave plasmas on the monocrystalline silicon piece. An analysis was also conducted to investigate the influence of methane concentration on the diamond film. When the methane concentration was set at 0.5%, the experiment turned out to have the high quality diamond film which was dense with homogeneous sizes. In condition that the methane concentration was 2.44%, the film obtained was much denser but with larger proportion of non-diamond components. In case that the methane concentration was about 0.25%, the purity of diamond film was declined while the film was inconsistent.

Abstract: The low temperature Raman spectroscopic (4000-95 cm^–1) investigation on the hydroxyl cobalt chloride Co₂(OH)₃Cl and deuteroxyl cobalt chloride Co₂(OD)₃Cl polycrystalline samples has been performed from the room temperature down to 4 K closing to the liquid Helium temperature. Lineshapes of Raman mode E_g (about 130 cm^–1 assigned to the normal symmetrically bending vibration mode of the [ClCo₃] group for both kinds of samples) are found to be apparently asymmetric Fano lineshapes when the temperatures are below 230 K. This phenomenon is preliminarily attributed to the effect of electron-phonon coupling and a continuum of electronic states centered at about 16 meV with an upper limit 18.5 meV is suggested in this report.

Abstract: Ag doped ZnO microrods are prepared on c-plane sapphire substrates by chemical vapour deposition method at high temperature.The morphology, structure and optical properties were investigated by scanning electron microscopy, X-ray diffraction and Raman spectrum, respectively. The prepared Ag doped ZnO microrods have good preferred orientation with very limited structural defects. The Raman bands indicates that a tensile stress existed in the sample and an additional local vibrational mode related to Ag is also found which can be used to confirm the existence of Ag in the Ag doped ZnO microrods.

Abstract: The radiation damage and its distribution in the type-Ib diamond film implanted by B ion have been investigated by means of Raman scattering and X-ray diffraction spectra. It is of significance during the applications of diamond materials due to several phenomena related to B-doped diamond, such as the superconductivity, the conversion of p-type to n-type conductivity and the low resistivity. The Raman scatting spectra indicated that the radiation damage in implantation layer was various with implantation depth. The top layer was damaged badly and graphitized completely. There existed small damage in nether layer, which resulted in partly amorphous carbon. It was noted that the volume was expanded in diamond film implanted by B ion. By x-ray diffraction pattern, it was reckoned that the lattice parameter was enlarged in B-implanting diamond layer, which expanded the volume of diamond film.

Abstract: Thermoelectric (TE) devices are increasingly being seen as having the potential to make important contributions to reducing greenhouse gas emissions and providing cleaner forms of energy. A number of articles have been devoted to the thermoelectric properties of materials. From the search for novel and effective thermoelectric materials the clathrate structures has emerged as one of the most promising candidates for achieving very high thermoelectric figure of merit: ZT= α²σT/κ, where α, T, σ and κ are the Seebeck coefficient, absolute temperature, electrical conductivity, and total thermal conductivity, respectively [1]. For the past decade, caged clathrate compounds of group IV elements have attracted much attention because they would possess a low k_L value as the theoretical minimum one, which results from rattling of atoms filled in their cages [2-3]. There are the type-I, type-III, and type-VIII structures in thermoelectric clathrates, but most compounds adopt type-I structure (space group No.223; Pm-3n). A large number of the type-I clathrates with the chemical formula of II₈III₁₆IV₃₀ (II=Ba, Sr, Eu, III=Al, Ga, In, and IV= Si, Ge, Sn) have been synthesized and studied intensively [5-11], which results in relatively high ZT values such as 0.7 at 700 K for Ba₈Ga₁₆Ge₃₀ and 0.87 at 870 K for Ba₈Ga₁₆Si₃₀ [3]. Among type-I clathrates, a single-crystal n-type Ba₈Ga₁₆Ge₃₀ grown using the Czochralski method with a ZT of 1.35 at 900 K is one of the most promising results [12].