Effects of Excitation Wavelength on the Raman Spectra of Vanadium(V) Oxo Compounds

Abstract In this work, we study the Raman spectra of twisted bilayer graphene samples as a function of their twist-angles (θ), ranging from 0.03º to 3.40º, where local θ are determined by analysis of their associated moiré superlattices, as imaged by scanning microwave impedance microscopy. Three standard excitation laser lines are used (457, 532, and 633 nm wavelengths), and the main Raman active graphene bands (G and 2D) are considered. Our results reveal that electron-phonon interaction influences the G band's linewidth close to the magic angle regardless of laser excitation wavelength. Also, the 2D band lineshape in the θ < 1º regime is dictated by crystal lattice and depends on both the Bernal (AB and BA) stacking bilayer graphene and strain soliton regions (SP) [1]. We propose a geometrical model to explain the 2D lineshape variations, and from it, we estimate the SP width when moving towards the magic angle.

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Effect of annealing temperature on optical and electrical properties of metallophthalocyanine thin films deposited on silicon substrate

Materials Science-Poland ◽

10.1515/msp-2016-0086 ◽

2016 ◽

Vol 34 (3) ◽

pp. 676-683 ◽

Cited By ~ 2

Author(s):

R. Skonieczny ◽

P. Popielarski ◽

W. Bała ◽

K. Fabisiak ◽

K. Paprocki ◽

...

Keyword(s):

Thin Films ◽

Raman Spectra ◽

Silicon Substrate ◽

Thin Layers ◽

Excitation Wavelength ◽

Type Silicon ◽

Atomic Force ◽

Before And After ◽

Evaporation Technique ◽

Polarized Raman

AbstractThe cobalt phthalocyanine (CoPc) thin films (300 nm thick) deposited on n-type silicon substrate have been studied using micro-Raman spectroscopy, atomic force spectroscopy (AFM) and I-V measurement. The CoPc thin layers have been deposited at room temperature by the quasi-molecular beam evaporation technique. The micro-Raman spectra of CoPc thin films have been recorded in the spectral range of 1000 cm-1 to 1900 cm-1 using 488 nm excitation wavelength. Moreover, using surface Raman mapping it was possible to obtain information about polymorphic forms distribution (before and after annealing) of metallophthalocyanine (α and β form) from polarized Raman spectra. The I-V characteristics of the Au/CoPc/n-Si/Al Schottky barrier were also investigated. The obtained results showed that influence of the annealing process plays a crucial role in the ordering and electrical conductivity of the molecular structure of CoPc thin films deposited on n-type silicon substrate.

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Dependence of the Raman spectra of drug substances upon laser excitation wavelength

Journal of Raman Spectroscopy ◽

10.1002/jrs.1446 ◽

2006 ◽

Vol 37 (1-3) ◽

pp. 335-341 ◽

Cited By ~ 18

Author(s):

Fiona C. Thorley ◽

Kurt J. Baldwin ◽

David C. Lee ◽

David N. Batchelder

Keyword(s):

Raman Spectra ◽

Laser Excitation ◽

Excitation Wavelength ◽

Drug Substances

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Decomposition of Mixed Phase Silicon Raman Spectra

MRS Proceedings ◽

10.1557/proc-1153-a02-03 ◽

2009 ◽

Vol 1153 ◽

Author(s):

Martin Ledinský ◽

Jiri Stuchlík ◽

Aliaksei Vetushka ◽

Antonin Fejfar ◽

Jan Kočka

Keyword(s):

Thin Film ◽

Factor Analysis ◽

Light Scattering ◽

Raman Spectra ◽

Absolute Intensity ◽

Mixed Phase ◽

Excitation Wavelength ◽

Microcrystalline Silicon ◽

Silicon Thin Film ◽

Spectral Components

AbstractSeries of Raman spectra were measured for microcrystalline silicon thin film with variable crystallinity. Five sets of Raman spectra (corresponding to excitations at 325 nm, 442 nm, 514.5 nm, 632.8 nm and 785 nm wavelengths) were subjected to factor analysis which showed that each set of spectra consisted of just two independent spectral components. Decomposition of the measured Raman spectra into the amorphous and the microcrystalline components is illustrated for 514.5 nm and 632.8 nm excitations. Effect of the light scattering on absolute intensity of Raman spectra was identified even for excitation wavelength highly absorbed in the mixed phase silicon layers.

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Excitation Wavelength Dependent Raman Scattering in Low and Highly Degenerate InN Films

MRS Proceedings ◽

10.1557/proc-831-e3.16 ◽

2004 ◽

Vol 831 ◽

Author(s):

V.M. Naik ◽

H. Dai ◽

R. Naik ◽

D.B. Haddad ◽

J.S. Thakur ◽

...

Keyword(s):

Molecular Beam Epitaxy ◽

Raman Scattering ◽

Excitation Energy ◽

Raman Spectra ◽

Molecular Beam ◽

Optical Bandgap ◽

Structural Defects ◽

Excitation Wavelength ◽

Phonon Modes ◽

Energy Mode

ABSTRACTThe Raman spectra of low and highly degenerate InN films grown by conventional Molecular Beam Epitaxy (MBE) and Plasma Source Molecular Beam Epitaxy (PSMBE) have been studied using visible (514.5 nm) and near infrared (785 nm) excitation wavelengths. The MBE grown InN films have a low electron carrier concentration, ne < 2.0 × 1019 cm−3, exhibiting an optical bandgap absorption edge of 0.6 to 0.7 eV. On the other hand PSMBE grown InN samples are highly degenerate with ne > 3 × 1020 cm−3 with an observed optical bandgap ranging from 1.5 to 1.9 eV. Raman spectra of low degenerate InN films show sharp E2 and A1(LO) modes whereas spectra of highly degenerate InN films show rather broad features indicating the presence of a large number of structural defects. In the latter samples a resonance enhanced Raman scattering is observed especially with 785 nm excitation energy, where the excitation energy matches the optical energy bandgap. Another interesting observation is that the expected coupled plasmon LO-phonon modes are not detected in these films, rather a phonon mode is observed at the location of the unscreened A1(LO) mode. The observation of unscreened LO-phonon, and the absence of coupled plasmon LO-phonon modes have been attributed to Landau damping of the higher energy mode and coupling of the lower energy mode with the electron-hole pair excitations leading to the emergence of a mode very close to the A1(LO) mode.

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RDX remote Raman detection on NATO SET-237 samples

The European Physical Journal Plus ◽

10.1140/epjp/s13360-021-01336-9 ◽

2021 ◽

Vol 136 (4) ◽

Author(s):

Emanuela C. A. Gallo ◽

Luca M. L. Cantu ◽

Frank Duschek

Keyword(s):

Raman Spectroscopy ◽

Excitation Energy ◽

Raman Spectra ◽

Ccd Camera ◽

Surface Concentration ◽

Remote Detection ◽

Excitation Wavelength ◽

Standard Samples ◽

Minimum Requirements

AbstractUltraviolet Raman spectroscopy measurements have been taken at DLR in Lampoldshausen to detect NATO SET-237 standard samples of RDX. The main goal was to quantify the minimum requirements for an unambiguous identification in remote detection (60 cm distance) with a commercial Czerny–Turner spectrometer coupled with a CCD camera. Well-defined distribution of explosives on surfaces was tested as standardized samples. Therefore, Raman spectra of RDX have been acquired for different sample concentrations (50, 250 and 1000 μg/cm2, respectively) and under several laser energies (1.5, 3.0 and 5.0 mJ/pulse, respectively) at 355 nm excitation wavelength. The lowest possible reproducible surface concentration (50 µg/cm2) was detected with excitation energy of 3 mJ/pulse in the described configuration.

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Hemoglobin oxygen saturation measurements using resonance Raman intravital microscopy

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01171.2004 ◽

2005 ◽

Vol 289 (1) ◽

pp. H488-H495 ◽

Cited By ~ 28

Author(s):

Ivo P. Torres Filho ◽

James Terner ◽

Roland N. Pittman ◽

Leonardo G. Somera ◽

Kevin R. Ward

Keyword(s):

Oxygen Saturation ◽

Raman Spectra ◽

Raman Band ◽

Ultraviolet Region ◽

Excitation Wavelength ◽

Isolated Cells ◽

Light Power ◽

Hemoglobin Oxygen Saturation ◽

Rat Mesentery

A system is described for in vivo noninvasive measurements of hemoglobin oxygen saturation (HbO2Sat) at the microscopic level. The spectroscopic basis for the application is resonant Raman enhancement of Hb in the violet/ultraviolet region, allowing simultaneous identification of oxy- and deoxyhemoglobin with the same excitation wavelength. The heme vibrational bands are well known, but the technique has never been used to determine microvascular HbO2Sat in vivo. A diode laser light (power: 0.3 mW) was focused onto sample areas 15–30 μm in diameter. Raman spectra were obtained in backscattering geometry by using a microscope coupled to a spectrometer and a cooled detector. Calibration was performed in vitro by using glass capillaries containing blood at several Hb concentrations, equilibrated at various oxygen tensions. HbO2Sat was estimated using the Raman band intensities at 1,360 and 1,375 cm−1. Glass capillary path length and Hb concentration had no effect on HbO2Sat estimated from Raman spectra. In vivo observations were made in blood flowing in microvessels of the rat mesentery. The Hb Raman peaks observed in oxygenated and deoxygenated blood were consistent with earlier Raman studies that used Hb solutions and isolated cells. The method allowed HbO2Sat determinations in the whole range of arterioles, venules, and capillaries. Tissue transillumination allowed diameter and erythrocyte velocity measurements in the same vessels. Raman microspectroscopy offers distinct advantages over other currently used techniques by providing noninvasive and reliable in vivo determinations of HbO2Sat in thin tissues as well as in solid organs and tissues, which are unsuitable for techniques requiring transillumination.

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