Investigation of Raman Modes and Born-Effective Charges in AgNb1/2 Ta1/2 O3 : A Density-Functional and Raman Scattering Study

2015 ◽  
Vol 99 (1) ◽  
pp. 332-339 ◽  
Author(s):  
Kotagiri Ganga Prasad ◽  
Manish K. Niranjan ◽  
Saket Asthana ◽  
R. Karthikeyan
Keyword(s):  
Raman Scattering ◽  
Density Functional ◽  
Raman Modes ◽  
Scattering Study ◽  
Effective Charges

scholarly journals Ultrasensitive molecular sensor using N-doped graphene through enhanced Raman scattering

2016 ◽  
Vol 2 (7) ◽  
pp. e1600322 ◽  
Author(s):  
Simin Feng ◽  
Maria Cristina dos Santos ◽  
Bruno R. Carvalho ◽  
Ruitao Lv ◽  
Qing Li ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Density Functional ◽  
Pristine Graphene ◽  
Research Attention ◽  
Nitrogen Doped ◽  
Raman Modes ◽  
Nitrogen Doped Graphene ◽  
Doped Graphene ◽  
Enhanced Raman Scattering ◽  
Homo Lumo

As a novel and efficient surface analysis technique, graphene-enhanced Raman scattering (GERS) has attracted increasing research attention in recent years. In particular, chemically doped graphene exhibits improved GERS effects when compared with pristine graphene for certain dyes, and it can be used to efficiently detect trace amounts of molecules. However, the GERS mechanism remains an open question. We present a comprehensive study on the GERS effect of pristine graphene and nitrogen-doped graphene. By controlling nitrogen doping, the Fermi level (EF) of graphene shifts, and if this shift aligns with the lowest unoccupied molecular orbital (LUMO) of a molecule, charge transfer is enhanced, thus significantly amplifying the molecule’s vibrational Raman modes. We confirmed these findings using different organic fluorescent molecules: rhodamine B, crystal violet, and methylene blue. The Raman signals from these dye molecules can be detected even for concentrations as low as 10−11M, thus providing outstanding molecular sensing capabilities. To explain our results, these nitrogen-doped graphene-molecule systems were modeled using dispersion-corrected density functional theory. Furthermore, we demonstrated that it is possible to determine the gaps between the highest occupied and the lowest unoccupied molecular orbitals (HOMO-LUMO) of different molecules when different laser excitations are used. Our simulated Raman spectra of the molecules also suggest that the measured Raman shifts come from the dyes that have an extra electron. This work demonstrates that nitrogen-doped graphene has enormous potential as a substrate when detecting low concentrations of molecules and could also allow for an effective identification of their HOMO-LUMO gaps.

scholarly journals Ab initio и экспериментальное исследование колебательных свойств кристаллов TlFeS-=SUB=-2-=/SUB=- и TlFeSe-=SUB=-2-=/SUB=-

2021 ◽  
Vol 63 (10) ◽  
pp. 1637
Author(s):  
З.А. Джахангирли ◽  
Р.Г. Велиев ◽  
И.А. Мамедова ◽  
З.И. Бадалова ◽  
Д.А. Мамедов ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Raman Scattering ◽  
Ab Initio ◽  
Density Functional ◽  
Vibrational Properties ◽  
Site Symmetry ◽  
Functional Theory ◽  
Infrared Reflection ◽  
Raman Modes ◽  
Ir Light

The lattice vibrational properties of TlFeS2 and TlFeSe2 crystals have been studied experimentally using Raman scattering (RS) and infrared reflection (IR) light, as well as theoretically using density functional theory (DFT). The complete vibrational representation, based on the analysis of the factor site symmetry, contains 12 active Raman modes and 9 IR active modes. 6 RS active and 3 IR active modes of them for TlFeS2, and 4 RS active and 3 IR active modes for TlFeSe2 were experimentally detected and identified.

Raman Scattering Study of H2O2-Etched Zn0.1Cd0.9Te Surfaces

1996 ◽  
Vol 450 ◽  
Author(s):  
Brajesh K. Rai ◽  
R. S. Katiyar ◽  
K. -T. Chen ◽  
H. Chen ◽  
A. Burger
Keyword(s):  
Raman Scattering ◽  
Quantum Confinement ◽  
Laser Power ◽  
Peak Position ◽  
Downward Shift ◽  
Te Precipitates ◽  
Raman Modes ◽  
Raman Study ◽  
Scattering Study ◽  
High Irradiation

ABSTRACTRaman study of as-grown and H2O2-etched surfaces of Zn0.1Cd0.9 Te single crystal has been performed. A distribution of Te precipitates on the surface of as-grown ZCT, which increases after etching, has been encountered. With high irradiation powers, due to the oxidation of the surfaces, new bands of TeO32− are evolved. A downward shift in the peak position, as well as a halfwidth broadening, of all Raman modes has been observed with increasing laser power. The phenomenon, due to the formation of insulating oxide of tellurium in a dispersion of Te precipitates and vice-versa, has been attributed to the quantum confinement of phonons.

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