Topic
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.
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TL;DR: In this article, the authors measured carrier relaxation times in epitaxial graphene layers grown on SiC wafers and found that an initial fast relaxation transient in the 70-120 fs range is followed by a slower relaxation process in the 0.4-1.7 ps range.
Abstract: Using ultrafast optical pump-probe spectroscopy, we have measured carrier relaxation times in epitaxial graphene layers grown on SiC wafers. We find two distinct time scales associated with the relaxation of nonequilibrium photogenerated carriers. An initial fast relaxation transient in the 70-120 fs range is followed by a slower relaxation process in the 0.4-1.7 ps range. The slower relaxation time is found to be inversely proportional to the degree of crystalline disorder in the graphene layers as measured by Raman spectroscopy. We relate the measured fast and slow time constants to carrier-carrier and carrier-phonon intraband and interband scattering processes in graphene.
413 citations
TL;DR: In this article, a glass fiber optical waveguide was used for the construction of wide-band fiber amplifiers and Raman oscillators tunable over a range of 100 A. Even though the Raman cross section is quite small, relatively low threshold for Raman emission can be achieved because high optical power densities are maintained over long lengths of waveguide.
Abstract: Stimulated Raman emission in the visible has been observed in glass‐fiber optical waveguides. Even though the Raman cross section is quite small, relatively low threshold for Raman emission can be achieved because high optical power densities are maintained over long lengths of waveguide. The broad stimulated gain bandwidths available in glass should permit the construction of wide‐band fiber amplifiers and Raman oscillators tunable over a range of 100 A.
412 citations
TL;DR: In this article, different techniques using a triple monochromator or a holographic grating system have been described to generate Raman images of heterogeneous samples of different substances.
Abstract: New devices, have been developed to generate maps or images of heterogeneous samples using a characteristic Raman frequency line and to obtain the surface distribution of a given compound.
Samples are illuminated by a laser beam causing Raman lines of the different substances to be emitted. Different techniques using a triple monochromator or a holographic grating system are described. Several examples of Raman images of heterogeneous samples are presented.
412 citations
TL;DR: A large area of highly-crystalline MoSe2 atomic layers are synthesized on SiO2/Si, mica and Si substrates using a simple chemical vapour deposition (CVD) method at atmospheric pressure, suggesting that MoSe 2 monolayer is a promising material for photodetection applications.
Abstract: Synthesis of large-area, atomically thin transition metal dichalcogenides (TMDs) on diverse substrates is of central importance for the large-scale fabrication of flexible devices and heterojunction-based devices. In this work, we successfully synthesized a large area of highly-crystalline MoSe2 atomic layers on SiO2/Si, mica and Si substrates using a simple chemical vapour deposition (CVD) method at atmospheric pressure. Atomic force microscopy (AFM) and Raman spectroscopy reveal that the as-grown ultrathin MoSe2 layers change from a single layer to a few layers. Photoluminescence (PL) spectroscopy demonstrates that while the multi-layer MoSe2 shows weak emission peaks, the monolayer has a much stronger emission peak at ∼1.56 eV, indicating the transition from an indirect to a direct bandgap. Transmission electron microscopy (TEM) analysis confirms the single-crystallinity of MoSe2 layers with a hexagonal structure. In addition, the photoresponse performance of photodetectors based on MoSe2 monolayer was studied for the first time. The devices exhibit a rapid response of ∼60 ms and a good photoresponsivity of ∼13 mA/W (using a 532 nm laser at an intensity of 1 mW mm−2 and a bias of 10 V), suggesting that MoSe2 monolayer is a promising material for photodetection applications.
412 citations
TL;DR: In this article, surface Raman scattering is used to study self-assembled monolayers formed from a series of 1-alkanethiol s, CH3(CH2)^SH, where n = 3-5, 7, 8,11, and 17, at mechanically polished and electrochemically roughened Au surfaces.
Abstract: Surface Raman scattering is used to study self-assembled monolayers formed from a series of 1-alkanethiol s, CH3(CH2)^SH, where n = 3-5, 7, 8,11, and 17, at mechanically polished and electrochemically roughened Au surfaces. Defect structure in these films is investigated by use of the relative intensities of peaks due to trans and gauche conformations in the v(C-S) and P(C-C) frequency regions. Surface selection rules for Raman spectroscopy are used to estimate orientation of the alkanethiol layers at Au. The orientation proposed on the basis of the Raman spectral data is consistent with those previously reported on the basis of other measurements at Au surfaces. This orientation is compared to that previously determined for these films at Ag. Alkanethiols at Ag are found to have a chain tilt from the surface normal less than the 30° previously reported for Au. The C-S bond is found to be perpendicular to the Ag surface while it is largely parallel to the surface at Au. Differences in the spectra of short-chain alkanethiols from smooth and rough surfaces are attributed to disordering of the film at the roughened Au surface which occurs predominantly near the S end of the molecule on rough Au surfaces.
411 citations