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Raman Peaks (raman + peak)
Selected AbstractsSoluble Graphene: Soluble Graphene: Generation of Aqueous Graphene Solutions Aided by a Perylenebisimide-Based Bolaamphiphile (Adv. Mater.ADVANCED MATERIALS, Issue 42 200942/2009) Single-layer graphene (SLG) can be deposited onto Si/SiO2 substrates from aqueous dispersions using a scalable and quick detergent-based method that takes advantage of the availability and low cost of graphite as a feedstock, report Andreas Hirsch and co-workers on p. 4265. The deposits were analyzed using absorption and Raman spectroscopy and atomic force and optical microscopy. Evaluation of the two-phonon defect-induced Raman peak of individual particles on the substrate was then used to confirm exfoliation into graphene monolayers. [source] Soluble Graphene: Generation of Aqueous Graphene Solutions Aided by a Perylenebisimide-Based BolaamphiphileADVANCED MATERIALS, Issue 42 2009Jan M. Englert Single-layer graphene (SLG) is deposited onto Si/SiO2 substrates from aqueous dispersions using a scalable and quick detergent-based method (see figure). The deposits are analyzed using absorption and Raman spectroscopy and atomic force and optical microscopy. Evaluation of the two-phonon defect-induced Raman peak of individual particles on the substrate is used to confirm exfoliation into graphene monolayers. [source] Correlating Raman peak shifts with phase transformation and defect densities: a comprehensive TEM and Raman study on siliconJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2009Thomas Wermelinger Abstract Silicon is the most often used material in micro electromechanical systems (MEMS). Detailed understanding of its mechanical properties as well as the microstructure is crucial for the reliability of MEMS devices. In this paper, we investigate the microstructure changes upon indentation of single crystalline (100) oriented silicon by transmission electron microscopy (TEM) and Raman microscopy. TEM cross sections were prepared by focused ion beam (FIB) at the location of the indent. Raman microscopy and TEM revealed the occurrence of phase transformations and residual stresses upon deformation. Raman microscopy was also used directly on the cross-sectional TEM lamella and thus microstructural details could be correlated to peak shape and peak position. The results show, however, that due to the implanted Ga+ ions in the lamella the silicon Raman peak is shifted significantly to lower wavenumbers. This hinders a quantitative analysis of residual stresses in the lamella. Furthermore, Raman microscopy also possesses the ability to map deformation structures with a lateral resolution in the submicron range. Copyright © 2009 John Wiley & Sons, Ltd. [source] Raman scattering probe of anharmonic effects in NiSiJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2004S. K. Donthu Abstract We report a systematic temperature-dependent Raman scattering study of NiSi thin films. In agreement with the basic anharmonic theory, the strong Raman peak from NiSi at about 214 cm,1 shows phonon softening and broadening with an increase in the sample temperature. Comparative study of the temperature dependence of this first-order Raman peak from NiSi powder and the film show that NiSi layers of thickness 15,90 nm are under tensile thermal stress. The results also show that the total phonon shift observed in the temperature range 80,500 K is independent of the silicide film thickness. We have also shown that Raman spectroscopy is a faster and more sensitive technique than x-ray diffraction for phase identification in NiSi nanolayers, hence Raman scattering can be used as a valuable tool for in situ growth and process monitoring of nickel silicides. Copyright © 2004 John Wiley & Sons, Ltd. [source] Applicability of laser-induced Raman microscopy for in situ monitoring of imine formation in a glass microfluidic chipJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2003Moonkwon Lee Abstract Laser-induced Raman microscopy has been used to illustrate its applicability for the in situ monitoring of imine formation reaction in a glass microfluidic chip. In order to monitor the diffusion process in a micro channel, the Raman spectra were measured at various points along the channel with a constant flow rate of 2.7 µl min,1. Time-dependent Raman spectra were also measured without flow in order to monitor the variation of Raman peaks to a complete conversion. The disappearance of the CO stretching peak at 1700 cm,1 of the reactant, benzaldehyde, and the appearance of the Raman peak for the product, an imine, at 1628 cm,1 were successfully monitored. In addition, the intensity increases of three phenyl stretching modes in the 1550,1630 cm,1 region were also observed. The increase in Raman intensity for this vibrational mode is caused by an effective ,-electron conjugation between two phenyl rings through the ,CN,bridging group of the product. Laser-induced Raman microscopy enables us to monitor in situ product formation and to obtain detailed structural information in a glass microfluidic chip. Copyright © 2003 John Wiley & Sons, Ltd. [source] Raman and transmission electron microscopy characterization of InN samples grown on GaN/Al2O3 by molecular beam epitaxyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006J. Arvanitidis Abstract Raman spectroscopy and transmission electron microscopy were employed to study the vibrational properties and the microstructure of epitaxially grown InN films on GaN/Al2O3 templates. The variations of the InN lattice constants, as deduced by electron diffraction analysis, along with the red-shifted E22 mode frequency reveal that InN films exhibit residual tensile stress, strongly dependent on the epilayer growth temperature. Threading dislocations are the dominant structural defects in the films, having a density in the order of 109,1010 cm,2. Profile analysis of the E22 Raman peak by means of the Spatial Correlation Model provides useful information concerning the effective mean length for free phonon propagation (L), which is a measure of the structural quality of the samples. In all the studied samples, L monotonically increases with decreasing threading dislocation density of pure screw and mixed type character. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Raman spectroscopic and X-ray investigation of stressed states in diamond-like carbon filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1-2 2005R. Krawietz Abstract The non-destructive characterization of intrinsic stress is very important to evaluate the reliability of devices based on diamond-like carbon (DLC) films. Whereas the only requirement for the X-ray diffraction method is a crystalline state of specimen, Raman spectroscopic stress analysis is restricted to materials showing intensive and sharp Raman peaks. On the other hand, Raman spectroscopy offers the possibility to measure stress profiles with lateral resolution of about 1 micron. The results of stress measurements in DLC films using both X-ray diffraction and Raman spectroscopy are found in very good correspondence. Mean stress in carbon films consisting of very small crystallites on silicon substrates has been determined by measuring and fitting the stress profiles in the substrate near artificial vertical film edges. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ab initio quantum-mechanical prediction of the IR and Raman spectra of Ca3Cr2Si3O12 Uvarovite garnetINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2010L. Valenzano Abstract The IR and Raman spectra of uvarovite (Ca3Cr2Si3O12) garnet were simulated with the periodic ab initio CRYSTAL code by adopting an all-electron Gaussian-type basis set and the B3LYP Hamiltonian. The two sets of 17 F1u Transverse-Optical (TO) and Longitudinal-Optical (LO) frequencies are generated, together with their intensities. As regards the IR experimental spectrum, only five peaks are available, that are in excellent agreement with the calculated data (mean absolute difference smaller than 5.2 cm,1). The analysis of the TO-LO eigenvalue overlaps permits to establish a correspondence between LO and TO modes. The set of experimental Raman peaks is much reacher (23 out of 25) and the agreement with our calculations excellent ( smaller than 6 cm,1). Isotopic substitution is used to identify the zones of the spectrum where Cr and Ca contributions are relevant. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Raman scattering studies of the magnetic ordering in hexagonal HoMnO3 thin filmsJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2010Nguyen Thi Minh Hien Abstract We present the results of the temperature dependence of the Raman spectra of hexagonal HoMnO3 thin films in the 13,300 K temperature range. The films were grown on Pt(111)//Al2O3 (0001) substrates using the laser ablation method. In the HoMnO3 thin films, we initially observedseveral broad Raman peaks at ,510, 760, 955, 1120, and 1410 cm,1. These broad Raman peaks display an anomalous behavior near the magnetic transition temperature, and the intensity difference of the Raman spectra at different temperatures shows several pairs of negative and positive peaks as the temperature is lowered below the Néel temperature. Our analyses indicate that all the broad peaks are correlated with magnetic ordering, and we have assigned the origin of all the broad peaks. Purely on the basis of the Raman analysis, we have deduced the Néel temperature and the spin exchange integrals of HoMnO3 thin films. We also investigated the effects of the growth condition on the strongest broad peak at ,760 cm,1, which is related with pure magnetic ordering. This result indicates that the oxygen defect in the HoMnO3 sample has negligible effect on magnetic ordering. Copyright © 2009 John Wiley & Sons, Ltd. [source] In vivo study on the protection of indole-3-carbinol (I3C) against the mouse acute alcoholic liver injury by micro-Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2009Aiguo Shen Abstract Micro-Raman spectroscopy (MRS) was utilized for the first time to evaluate the effect of indole-3-carbinol (I3C) on acute alcoholic liver injury in vivo. In situ Raman analysis of tissue sections provided distinct spectra that can be used to distinguish alcoholic liver injury as well as ethanol-induced liver fibrosis from the normal state. Sixteen mice with liver diseases including acute liver injury and chronic liver fibrosis, and eight mice with normal liver tissues, and eight remedial mice were studied employing the Raman spectroscopic technique in conjunction with biomedical assays. The biochemical changes in mouse liver tissue when liver injury/fibrosis occurs such as the loss of reduced glutathione (GSH), and the increase of collagen (,-helix protein) were observed by MRS. The intensity ratio of two Raman peaks (I1450/I666) and in combination with statistical analysis of the entire Raman spectrum was found capable of classifying liver tissues with different pathological features. Raman spectroscopy therefore is an important candidate for a nondestructive in vivo screening of the effect of drug treatment on liver disease, which potentially decreases the time-consuming clinical trials. Copyright © 2008 John Wiley & Sons, Ltd. [source] Fluorescence and Raman spectra on painting materials: reconstruction of spectra with mathematical methodsJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2006Iacopo Osticioli Abstract SERDS (shift excitation difference spectroscopy) and SSRS (subtracted shifted Raman spectroscopy) methods were applied for fluorescence-background rejection in the Raman spectra of colored materials. These techniques are based on the assumption that the fluorescence contribution can be completely eliminated by subtracting two Raman spectra acquired at two shifted laser excitation frequencies. For the SERDS method a micro-Raman experimental apparatus coupled with a tunable diode laser (central emission at 684 nm) was set up. SSRS measurements were made on a commercial micro-Raman instrument; in this case the shifted spectrum was obtained by moving the spectrometer grating. Raman spectra were then reconstructed by applying the difference deconvolution method that automatically converts the difference signals in Raman peaks through a deconvolution operation. These techniques were tested on two reference colors (ultramarine and 6,6,-dibromoindigotine) and two colored samples of unknown composition (a Pompeian pink powder and a blue paint from a XVII century painting). Fluorescence-background subtraction and the following operation of spectra reconstruction took place successfully with no errors in Raman peaks, width and wavenumber position. In addition, even weak spectral details were revealed favoring the comparison with reference data for a molecular identification. Copyright © 2006 John Wiley & Sons, Ltd. [source] In situ Raman scattering studies of high-pressure stability and transformations in the matrix of a nanostructured glass,ceramic compositeJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2005Kristina E. Lipinska-Kalita Abstract High-pressure Raman scattering studies have been performed on a glass-based composite consisting of nanometer-sized gallium oxide aggregates embedded in a potassium-silicate host glass using the diamond anvil cell technique. The Raman spectra of this heterophase nanocomposite showed a range of pressure-induced structural transformations occurring in the glass matrix. Compression from ambient pressure up to 10.8 GPa indicated a progressive reduction in the width of the intertetrahedral SiOSi angle distribution, which was completely reversible on decompression to ambient pressure. At higher pressures, the Raman spectra demonstrated a breakdown of the intermediate-range order in the glass matrix of the nanocomposite. The enhancement of scattering intensity in the region of the D-defect band at 565 cm,1 together with the blue shift of the main SiOSi symmetric stretching wavenumber are evidence of a permanent reduction in SiO4 ring statistics toward smaller-than-six-ring configurations in the three-dimensional glass network. Starting from 13 GPa, the Raman spectra displayed a remarkable decrease in the scattering intensity of the SiOSi symmetric stretching that has been related to a coordination change of the silicon atom. The Raman spectrum of the composite quenched from 23 GPa to ambient conditions illustrated the pressure-driven, permanent reconstructive modification of the glass matrix in the nanocomposite. The pressure-induced evolution of the Raman peaks assigned to the gallium oxide phase indicated a progressive densification of the nanocrystalline phase, reversible on decompression to ambient pressure. Copyright © 2005 John Wiley & Sons, Ltd. [source] Applicability of laser-induced Raman microscopy for in situ monitoring of imine formation in a glass microfluidic chipJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2003Moonkwon Lee Abstract Laser-induced Raman microscopy has been used to illustrate its applicability for the in situ monitoring of imine formation reaction in a glass microfluidic chip. In order to monitor the diffusion process in a micro channel, the Raman spectra were measured at various points along the channel with a constant flow rate of 2.7 µl min,1. Time-dependent Raman spectra were also measured without flow in order to monitor the variation of Raman peaks to a complete conversion. The disappearance of the CO stretching peak at 1700 cm,1 of the reactant, benzaldehyde, and the appearance of the Raman peak for the product, an imine, at 1628 cm,1 were successfully monitored. In addition, the intensity increases of three phenyl stretching modes in the 1550,1630 cm,1 region were also observed. The increase in Raman intensity for this vibrational mode is caused by an effective ,-electron conjugation between two phenyl rings through the ,CN,bridging group of the product. Laser-induced Raman microscopy enables us to monitor in situ product formation and to obtain detailed structural information in a glass microfluidic chip. Copyright © 2003 John Wiley & Sons, Ltd. [source] X-ray diffraction and Raman study of nanogranular BaTiO3,CoFe2O4 thin films deposited by laser ablation on Si/Pt substratesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2007J. Barbosa Abstract Nanocomposite thin films composed by (BaTiO3)1,x,(CoFe2O4)x with different cobalt ferrite concentrations (x) have been deposited by pulsed laser ablation on platinum covered Si(001) substrates. The films structure was studied by X-ray diffraction and Raman spectroscopy. It was found that the CoFe2O4 phase unit cell was compressed along the growth direction of the films, and it relaxed with increasing x. The opposite behavior was observed in the BaTiO3 phase where the lattice parameters obtained from the X-ray measurements presented a progressive distortion of its unit cell with increasing x. The presence of the strain in the films induced a blueshift of the Raman peaks of CoFe2O4 that decreased with increasing CoFe2O4 concentration. Cation disorder in the cobalt ferrite was observed for lower x, where the nanograins are more isolated and subjected to more strain, which was progressively decreased for higher CoFe2O4 content in the films. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High pressure studies of the radial breathing modes in double-wall carbon nanotubesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2007J. Arvanitidis Abstract This work focuses on the high pressure Raman study of the radial breathing modes (RBMs) of bundled double-wall carbon nanotubes (DWCNTs) using different excitation energies. The detailed examination of the Raman peaks attributed to the RBMs of the inner and outer tubes comprising the DWCNTs as a function of pressure provides a wealth of information concerning the pressure response of individual nanotubes as well as the inner-outer tube (intratube) interactions. The outer tube acts as a protection shield for the inner tube whereas the latter increase the structural stability of the externals upon pressure application. More importantly, the pressure response of the inner tubes, expressed by the normalized pressure slopes ,i = (1/,i) (,,i /,P) vs. frequency of their RBMs, shows a remarkable grouping in quasi-linear distributions wherein ,i increases with ,. This behavior is explained by assuming that the pressure response of an internal tube is crucially dependent on the intratube spacing and thus the structural characteristics of the encapsulating tube. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||