Raman spectroscopy

About: Raman spectroscopy is a research topic. Over the lifetime, 122605 publications have been published within this topic receiving 2891083 citations. The topic is also known as: Raman Spectrum Analysis & spectrum Analysis, Raman.

Raman Techniques: Fundamentals and Frontiers

Abstract: Driven by applications in chemical sensing, biological imaging and material characterisation, Raman spectroscopies are attracting growing interest from a variety of scientific disciplines The Raman effect originates from the inelastic scattering of light, and it can directly probe vibration/rotational-vibration states in molecules and materials Despite numerous advantages over infrared spectroscopy, spontaneous Raman scattering is very weak, and consequently, a variety of enhanced Raman spectroscopic techniques have emerged These techniques include stimulated Raman scattering and coherent anti-Stokes Raman scattering, as well as surface- and tip-enhanced Raman scattering spectroscopies The present review provides the reader with an understanding of the fundamental physics that govern the Raman effect and its advantages, limitations and applications The review also highlights the key experimental considerations for implementing the main experimental Raman spectroscopic techniques The relevant data analysis methods and some of the most recent advances related to the Raman effect are finally presented This review constitutes a practical introduction to the science of Raman spectroscopy; it also highlights recent and promising directions of future research developments

Raman spectra of epitaxial graphene on SiC and of epitaxial graphene transferred to SiO2

Abstract: Raman spectra were measured for mono-, bi- and trilayer graphene grown on SiC by solid state graphitization, whereby the number of layers was pre-assigned by angle-resolved ultraviolet photoemission spectroscopy. It was found that the only unambiguous fingerprint in Raman spectroscopy to identify the number of layers for graphene on SiC(0001) is the linewidth of the 2D (or D*) peak. The Raman spectra of epitaxial graphene show significant differences as compared to micromechanically cleaved graphene obtained from highly oriented pyrolytic graphite crystals. The G peak is found to be blue-shifted. The 2D peak does not exhibit any obvious shoulder structures but it is much broader and almost resembles a single-peak even for multilayers. Flakes of epitaxial graphene were transferred from SiC onto SiO2 for further Raman studies. A comparison of the Raman data obtained for graphene on SiC with data for epitaxial graphene transferred to SiO2 reveals that the G peak blue-shift is clearly due to the SiC substrate. The broadened 2D peak however stems from the graphene structure itself and not from the substrate.

Raman and infrared spectra of multiferroic bismuth ferrite from first principles

Abstract: The entire zone-center phonon spectrum of the $R3c$ ferroelectric antiferromagnetic phase of bismuth ferrite is computed using a first-principles approach based on density functional theory. Two phonon modes exhibiting eigendisplacement vectors that strongly overlap with the atomic distortions taking place at the ferroelectric structural phase transition are identified and give support to a transition with displacive character. Both Raman and infrared reflectivity spectra are also computed, providing benchmark theoretical results for the assignment of experimental spectra.

Stress measurements in silicon devices through Raman spectroscopy: Bridging the gap between theory and experiment

Abstract: The different steps that have to be taken in order to derive information about local mechanical stress in silicon using micro‐Raman spectroscopy experiments, including theoretical and experimental aspects, are discussed. It is shown that the calculations are in general less complicated when they are done in the axes system of the sample. For that purpose, the secular equation is calculated in the axes system [110], [−110], [001], which is important for microelectronics structures. The theory relating Raman mode shift with stress tensor components is applied using two analytical stress models: uniaxial stress and planar stress. The results of these models are fitted to data from micro‐Raman spectroscopy experiments on Si3N4/poly‐Si lines on silicon substrate. In this fit procedure, the dimensions of the laser spot and its penetration depth in the substrate are also taken into account.

Effective Rejection of Fluorescence Interference in Raman Spectroscopy Using a Shifted Excitation Difference Technique

Abstract: Resonance Raman spectroscopy is a powerful technique for probing the vibrations of particular chromophores in multicomponent systems. By tuning the wavelength of the excitation laser into resonance with an electronic absorption band of only one molecular species, the vibrational Raman scattering from this species can be selectively enhanced. Thus, resonance Raman spectroscopy can provide structural information for chromophores in solution or biological chromophores within their functionally active protein environment. However, since the very nature of the experiment requires that the excitation light be absorbed by the sample, the measurement of resonance Raman spectra is often made difficult by a large fluorescence background in the same spectral region as the Raman scattering. The problem of fluorescence interference from intrinsic sample emission is often further exacerbated in biological samples, where low-concentration impurities with large fluorescence yields can be difficult to remove. Even weak fluorescence, with an effective fluorescence quantum yield of ≈10−4, completely overwhelms resonance Raman signals, which have typical quantum yields of ≈10−7.