Special Issue "Raman Spectroscopy of Crystals"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: closed (2 September 2019).

Special Issue Editor

Dr. Alexander S. Krylov
E-Mail Website
Guest Editor
Laboratory of Molecular Spectroscopy, L. V. Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Academgorodok 50/38, Krasnoyarsk, 660036, Russia
Interests: Raman spectroscopy; ferroelectrics; high hydrostatic pressure; extreme condition; structural phase transition; multiferroics

Special Issue Information

Dear Colleagues,

Raman spectroscopy is now finding wide-ranging application in pure and applied science and can be used for the characterisation of the atomic structure of solids, because Raman scattering depends on the polarisation and direction of the incident light, the crystal symmetry and orientation of the solid sample, and the direction and polarisation of the scattered light. Raman spectroscopy can play a significant role in the study of crystal phase transformations, and it could involve order–disorder phenomena, polymorphs, chemical diffusion, and solid-solution shifts. One can study crystals in situ in extreme conditions—under high pressure, at high temperatures or both simultaneously, at low temperatures, or in electric or magnetic fields—and extract thermodynamic data from the variations in the Raman bands with varying pressure–temperature–field conditions. Other aspects that merit attention are the possibility of analysing nanocrystals, shocked crystals, crystalline microinclusions below the surface and many others.

The Special Issue on the “Raman Spectroscopy of Crystals” is devoted to theoretical and experimental, basic and applied research into all aspects utilising Raman spectroscopy to investigate processes in crystals and crystal properties. Scientists are encouraged to submit their manuscripts to this issue. The topics summarised in the keywords cover prime examples, but other related topics are also welcome. The volume is open for any contributions involving the Raman spectroscopy of crystalline matter.

Dr. Alexander S. Krylov
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Raman spectroscopy of solid and liquid crystals
  • structural phase transition and lattice dynamics
  • soft modes
  • extreme conditions: high pressure, temperature
  • magnetic and electric field

Published Papers (7 papers)

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Research

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Open AccessArticle
The Behavior of NH3+ Torsional Vibration in Amino Acids: A Raman Spectroscopic Study
Crystals 2019, 9(10), 517; https://doi.org/10.3390/cryst9100517 - 09 Oct 2019
Abstract
In this work we present the continuation of studies carried out on the changes of geometric parameters of the hydrogen bonds in amino acid crystals subjected to temperature or pressure variations. Changes in geometric parameters of the hydrogen bonds are correlated with the [...] Read more.
In this work we present the continuation of studies carried out on the changes of geometric parameters of the hydrogen bonds in amino acid crystals subjected to temperature or pressure variations. Changes in geometric parameters of the hydrogen bonds are correlated with the temperature behavior of the Raman wavenumber of NH3+ torsional band. Now four monocrystals, L-valine, L-isoleucine, taurine, and L-arginine hydrochloride monohydrate, are studied. Temperature evolution of the Raman wavenumber of NH3+ torsional band, with positive slope (dν/dT = 0.023 cm−1/K) of L-isoleucine, can be related to the stability of the crystal structure and the hydrogen bonds strengths on heating due to different temperature lattice parameters variation. Full article
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
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Open AccessArticle
Characterization of Coals and Coal Ashes with High Si Content Using Combined Second-Derivative Infrared Spectroscopy and Raman Spectroscopy
Crystals 2019, 9(10), 513; https://doi.org/10.3390/cryst9100513 - 02 Oct 2019
Abstract
The organic and mineral components in two coals and resulting high-temperature ashes with high silicon content were characterized by second-derivative infrared spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). The infrared spectra of raw coals show weak organic functional groups bands but strong kaolinite [...] Read more.
The organic and mineral components in two coals and resulting high-temperature ashes with high silicon content were characterized by second-derivative infrared spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). The infrared spectra of raw coals show weak organic functional groups bands but strong kaolinite bands because of the relatively high silicates content. In contrast, the Raman spectra of raw coals show strong disordered carbon bands but no mineral bands since Raman spectroscopy is highly sensitive to carbonaceous phases. The overlapping bands of mineral components (e.g., calcite, feldspar, and muscovite) were successfully resolved by the method of second-derivative infrared spectroscopy. The results of infrared spectra indicate the presence of metakaolinite in coal ashes, suggesting the thermal transformation of kaolinite during ashing. Intense quartz bands were shown in both infrared and Raman spectra of coal ashes. In addition, Raman spectra of coal ashes show a very strong characteristic band of anatase (149 cm–1), although the titanium oxides content is very low. Combined use of second-derivative infrared spectroscopy and Raman spectroscopy provides valuable insight into the analyses of mineralogical composition. The XRD results generally agree with those of FTIR and Raman spectroscopic analyses. Full article
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
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Open AccessArticle
Raman Characterization of Carrier Concentrations of Al-implanted 4H-SiC with Low Carrier Concentration by Photo-Generated Carrier Effect
Crystals 2019, 9(8), 428; https://doi.org/10.3390/cryst9080428 - 17 Aug 2019
Abstract
In this work, 4H SiC samples with a multilayer structure (shallow implanted layer in a lowly doped n-type epitaxial layer grown on a highly doped thick substrate) were investigated by Raman scattering. First, Raman depth profiling was performed to identify characteristic peaks for [...] Read more.
In this work, 4H SiC samples with a multilayer structure (shallow implanted layer in a lowly doped n-type epitaxial layer grown on a highly doped thick substrate) were investigated by Raman scattering. First, Raman depth profiling was performed to identify characteristic peaks for the different layers. Then, Raman scattering was used to characterize the carrier concentration of the samples. In contrast to the conventional Raman scattering measuring method of the Longitudinal Optical Plasmon Coupled (LOPC) mode, which is only suitable to characterize carrier concentrations in the range from 2 × 1016 to 5 × 1018 cm−3, in this work, Raman scattering, which is based on exciting photons with an energy above the band gap of 4H-SiC, was used. The proposed method was evaluated and approved for different Al-implanted samples. It was found that with increasing laser power the Al-implanted layers lead to a consistent redshift of the LOPC Raman peak compared to the peak of the non-implanted layer, which might be explained by a consistent change in effective photo-generated carrier concentration. Besides, it could be demonstrated that the lower concentration limit of the conventional approach can be extended to a value of 5 × 1015 cm−3 with the approach presented here. Full article
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
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Open AccessArticle
Polarization Dependence of Low-Frequency Vibrations from Multiple Faces in an Organic Single Crystal
Crystals 2019, 9(8), 425; https://doi.org/10.3390/cryst9080425 - 16 Aug 2019
Cited by 1
Abstract
Recent developments in optical filters have enabled the facile use of Raman spectroscopy for detection of low frequency (LF) vibrational modes. LF-Raman spectroscopy offers fast and sensitive characterization of LF vibrations, and enables the measurement of single microcrystals and detection of defects. It [...] Read more.
Recent developments in optical filters have enabled the facile use of Raman spectroscopy for detection of low frequency (LF) vibrational modes. LF-Raman spectroscopy offers fast and sensitive characterization of LF vibrations, and enables the measurement of single microcrystals and detection of defects. It is useful for probing intermolecular interactions in crystals, which are lower in energy, such as hydrogen bonds, shear modes, and breathing modes. Crystal excitation from multiple faces allows learning the orientation of intermolecular interactions, as polarization dependence varies with the polarizability of the interactions along the planes. Elucidating the orientations of the intermolecular interactions in organic crystals is essential for guiding the reactions or adsorption to a specific crystal face. In this study, we investigated the dependence of the LF-Raman signal intensity on the orientation of an organic single microcrystal of L-alanine. Three incident beam directions provided the orientations of the intermolecular interactions by analyzing the corresponding LF-Raman spectra. The signal intensity correlated well with the proximity between the incident beam’s direction and the orientations of the intermolecular interactions. Excellent compatibility was found between the spectra and simulated orientations based on structural information. Full article
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
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Open AccessArticle
Anomalous Behaviors of Spin Waves Studied by Inelastic Light Scattering
Crystals 2019, 9(7), 357; https://doi.org/10.3390/cryst9070357 - 14 Jul 2019
Abstract
Magnonics, an emerging research field, aims to control and manipulate spin waves in magnetic materials and structures. However, the current understanding of spin waves remains quite limited. This review attempts to provide an overview of the anomalous behaviors of spin waves in various [...] Read more.
Magnonics, an emerging research field, aims to control and manipulate spin waves in magnetic materials and structures. However, the current understanding of spin waves remains quite limited. This review attempts to provide an overview of the anomalous behaviors of spin waves in various types of magnetic materials observed thus far by inelastic light scattering experiments. The anomalously large asymmetry of anti-Stokes to Stokes intensity ratio, broad linewidth, strong resonance effect, unique polarization selection, and abnormal impurity dependence of spin waves are discussed. In addition, the mechanisms of these anomalous behaviors of spin waves are proposed. Full article
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
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Open AccessArticle
Resonance Raman Spectroscopy of Mn-Mgk Cation Complexes in GaN
Crystals 2019, 9(5), 235; https://doi.org/10.3390/cryst9050235 - 04 May 2019
Abstract
Resonance Raman analysis is performed in order to gain insight into the nature of impurity-induced Raman features in GaN:(Mn,Mg) hosting Mn-Mgk cation complexes and representing a prospective strategic material for the realization of full-nitride photonic devices emitting in the infra-red. It is [...] Read more.
Resonance Raman analysis is performed in order to gain insight into the nature of impurity-induced Raman features in GaN:(Mn,Mg) hosting Mn-Mgk cation complexes and representing a prospective strategic material for the realization of full-nitride photonic devices emitting in the infra-red. It is found that in contrast to the case of GaN:Mn, the resonance enhancement of Mn-induced modes at sub-band excitation in Mg co-doped samples is not observed at an excitation of 2.4 eV, but shifts to lower energies, an effect explained by a resonance process involving photoionization of a hole from the donor level of Mn to the valence band of GaN. Selective excitation within the resonance Raman conditions allows the structure of the main Mn-induced phonon band at ~670 cm−1 to be resolved into two distinct components, whose relative intensity varies with the Mg/Mn ratio and correlates with the concentration of different Mn-Mgk cation complexes. Moreover, from the relative intensity of the 2LO and 1LO Raman resonances at inter-band excitation energy, the Huang-Rhys parameter has been estimated and, consequently, the strength of the electron-phonon interaction, which is found to increase linearly with the Mg/Mn ratio. Selective temperature-dependent enhancement of the high-order multiphonon peaks is due to variation in resonance conditions of exciton-mediated outgoing resonance Raman scattering by detuning the band gap. Full article
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
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Review

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Open AccessReview
Raman Scattering in Non-Stoichiometric Lithium Niobate Crystals with a Low Photorefractive Effect
Crystals 2019, 9(10), 535; https://doi.org/10.3390/cryst9100535 - 17 Oct 2019
Abstract
Raman spectra of lithium niobate single crystals strongly doped by zinc and magnesium, it has been established, contain low-intense bands with frequencies 209, 230, 298, 694, and 880 cm−1. Ab ignition calculations fail to attribute these bands to fundamental vibrations of [...] Read more.
Raman spectra of lithium niobate single crystals strongly doped by zinc and magnesium, it has been established, contain low-intense bands with frequencies 209, 230, 298, 694, and 880 cm−1. Ab ignition calculations fail to attribute these bands to fundamental vibrations of A2 symmetry type unambiguously. Such vibrations are prohibited by the selection rules in the space group С3V6 (R3c). Ab initio calculations also proved that low-intense “extra” bands with frequencies 104 and 119 cm−1 definitely do not correspond to vibrations of A2 symmetry type. We have paid special attention to these extra bands that appear in LiNbO3 single crystals Raman spectra despite the fact that they are prohibited by the selection rules. In order to do so, we have studied a number of lithium niobate single crystals, both nominally pure and doped, by Raman spectroscopy. We have assumed that some “extra” bands correspond to two-particle states of acoustic phonons with a total wave vector equal to zero. We have also detected a Zn concentration area (0.05 – 0.94 mol.% ZnO in a crystal) where doped crystal structure is more ordered: The order of alternation of the main, doping cations, and vacancies along the polar axis is increased, and oxygen octahedra are less distorted. Full article
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
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