Longitudinal optical-transverse optical (L.O.-T.O.) splitting on internal modes in the Raman spectra of noncentric crystals

1987 ◽  
Vol 17 (4) ◽  
pp. 431-484 ◽  
Author(s):  
R. Durman ◽  
P. Favre ◽  
U. A. Jayasooriya ◽  
S. F. A. Kettle
Keyword(s):  
Raman Spectra ◽  
Longitudinal Optical ◽  
Transverse Optical

Nondestructive Characterizations of Au-Catalyzed GaAs Nanowires on GaAs(111)B Substrates via Identifications of 1st Order Optical Phonon Modes Using μ-Raman Spectroscopy

2020 ◽  
Vol 20 (7) ◽  
pp. 4358-4363
Author(s):  
Jeung Hun Park ◽  
Richard S. Kim ◽  
Se-Jeong Park ◽  
Gye-Choon Park ◽  
Choong-Heui Chung
Keyword(s):  
Raman Spectroscopy ◽  
Dose Rate ◽  
Raman Spectra ◽  
Optical Phonon ◽  
Longitudinal Optical ◽  
Transverse Optical ◽  
Longitudinal Optical Phonon ◽  
Phonon Modes ◽  
Gaas Nanowires ◽  
Beam Dose

We report the relation between the catalyst patterning conditions and the intensity of the 1st order Raman active modes in Au-catalyzed GaAs nanowire bundles. We fabricated e-beam lithographically Au-patterned GaAs(111)B substrates by varying the patterning conditions (e-beam dose rate, dot-size and interdot-spacings), and grew GaAs nanowires via vapor–liquid–solid process using a solid-source molecular beam epitaxy. To understand the effects of the substrate preparation conditions and resulting morphologies on the optical characteristics of 1st order transverse optical and longitudinal optical phonon modes of GaAs, we characterized the nanowire bundles using complementary μ-Raman spectroscopy and scanning electron microscopy as a function of the e-beam dose rate (145–595 μC/cm2), inter-dot spacing (100 and 150 nm) and pattern size (100 and 150 nm). Ensembles of single crystalline GaAs nanowires covered with different Au-thickness exhibit a downshift and asymmetric broadening of the 1st order transverse optical and longitudinal optical phonon peaks relative to GaAs bulk modes. We also showed that the sensitivity of a downshift and broadening of Raman spectra are directly related to morphological and surface coverage variations in as-grown nanowires. We observed clear increases of the transverse optical and longitudinal optical intensity as well as the relatively higher peak shift and broadening of Raman spectra from the 100 nm patterning in response to the dose rate change. Strong dependence of Raman spectra of the nanowire bundles on the e-beam dose rate changes are attributed to the variations in spatial density, size, shape and random growth orientation of the wires. We have shown that the identification of the changes in GaAs longitudinal optical and Arsenic anti-site peaks is good indicators to characterize the quality of as-grown GaAs nanowires. Our finding confirms the utilization of Raman spectroscopy as a powerful tool for characterizing chemical, structural, and morphological information of as-grown nanowires within the supporting substrate.

Polarized Raman spectra of an oriented single crystal of barium nitrite monohydrate

1983 ◽  
Vol 61 (3) ◽  
pp. 608-612 ◽  
Author(s):  
O. P. Lamba ◽  
H. D. Bist ◽  
Y. S. Jain
Keyword(s):  
Single Crystal ◽  
Raman Spectra ◽  
Longitudinal Optical ◽  
Transverse Optical ◽  
Polarized Raman ◽  
First Time ◽  
Barium Nitrite ◽  
Lattice Modes ◽  
Oriented Single Crystal

The symmetries of the observed Raman lines in the 4000–30 cm−1 region in different orientations of a single crystal of Ba(NO2)2•H2O have been determined and the spectra have been analysed in terms of the phonons originating from the internal modes of the NO2− and H2O groups and the external lattice modes. The longitudinal-optical and transverse-optical (LO–TO) splittings arising from the Coulomb forces in the crystal arc reported for the first time.

Raman Investigation of Heavily Al Doped 4H-SiC Layers Grown by CVD

2014 ◽  
Vol 806 ◽  
pp. 51-55 ◽  
Author(s):  
Pawel Kwasnicki ◽  
Roxana Arvinte ◽  
Hervé Peyre ◽  
Marcin Zielinski ◽  
Leszek Konczewicz ◽  
...  
Keyword(s):  
Carrier Concentration ◽  
Raman Spectra ◽  
Secondary Ion Mass Spectrometry ◽  
Low Frequency ◽  
Electrical Measurement ◽  
Longitudinal Optical ◽  
Electronic Transitions ◽  
Longitudinal Optical Phonon ◽  
Phonon Modes ◽  
The Continuum

In this work, we focus on heavily aluminum (Al) doped 4H-SiC samples. We compare the effect of the Al concentration and Hall carrier concentration on the Raman spectra in a large frequency range. The Al concentration measured by Secondary Ion Mass Spectrometry ranged from 2×1016to 8.4×1019cm-3while the electrical measurement give a carrier concentration up to 5×1019Al×cm-3. On the Raman spectra, three different frequency domains have been analysed: i) at high frequency where we consider the change in longitudinal optical phonon-plasmon coupled mode; ii°) at low frequency where we consider the continuum of electronic transitions and iii°) finally, considering the Fano interference effect between the continuum of electronic transitions and the Folded Transverse Acoustic phonon modes. This analysis is applied to comment a Raman spectra mapping collected on a 4H-SiC 2 inch wafer.

Raman analysis of the E1 and A1 quasi-longitudinal optical and quasi-transverse optical modes in wurtzite AlN

1999 ◽  
Vol 85 (7) ◽  
pp. 3535-3539 ◽  
Author(s):  
Leah Bergman ◽  
Mitra Dutta ◽  
Cengiz Balkas ◽  
Robert F. Davis ◽  
James A. Christman ◽  
...  
Keyword(s):  
Longitudinal Optical ◽  
Transverse Optical ◽  
Raman Analysis ◽  
Optical Modes

Raman spectra of CdS nanocrystals in Nafion: longitudinal optical and confined acoustic phonon modes

2001 ◽  
Vol 11 (4) ◽  
pp. 377-383 ◽  
Author(s):  
P Nandakumar ◽  
C Vijayan ◽  
M Rajalakshmi ◽  
Akhilesh K Arora ◽  
Y.V.G.S Murti
Keyword(s):  
Raman Spectra ◽  
Acoustic Phonon ◽  
Longitudinal Optical ◽  
Phonon Modes ◽  
Cds Nanocrystals
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