Investigation of Temperature and Composition Dependence of Relaxor Ferroelectric (1-x)PZN :xPT Using Micro-Raman Spectroscopy

1998 ◽  
Vol 547 ◽  
Author(s):  
S. Gupta ◽  
R.S. Katiyar ◽  
A. S. Bhalla
Keyword(s):  
Raman Spectra ◽  
Composition Dependence ◽  
Phonon Frequency ◽  
Soft Mode ◽  
Relaxor Ferroelectric ◽  
Frequency Range ◽  
Multiple Phase ◽  
Integrated Intensity ◽  
Frequency Position ◽  
Raman Modes

AbstractMicro-Raman spectra of relaxor ferroelectric (RFE) in the (1-x)Pb(Zn1/3Nb2/3)O3 :xTiO3 solid solution series have been measured as a function of temperature (70-580K) and composition (x = 0.02, 0.085, and 0.11). Micro-Raman spectra have been recorded in frequency range of 30-1000cm-1 and have been analyzed for all the Raman modes observed in terms of integrated intensity, phonon width and phonon frequency position. No soft mode like behavior is observed in the measured frequency range. We do observe two multiple phase transitions at 67°C (340K) and 147°C (420K) for the composition ≤ 0.91PZN:09PT, but both the transitions are slightly diffused in nature.

Strain Shift Coefficients for Phonons in Si-Ge Heterostructures

1991 ◽  
Vol 239 ◽  
Author(s):  
J.-M. Baribeau ◽  
D. J. Lockwood
Keyword(s):  
Molecular Beam ◽  
Composition Dependence ◽  
Vibration Mode ◽  
Phonon Frequency ◽  
Longitudinal Optical ◽  
Stress Factor ◽  
Double Crystal ◽  
Raman Scattering Spectroscopy ◽  
X Ray ◽  
Shift Coefficient

ABSTRACTStrain shift coefficient measurements for longitudinal optical phonons in molecular beam epitaxy grown metastable pseudomorphic Si1−xGex layers on (100) Si (0 < x < 0.35) and Ge (0.80 < x < 1) are reported. Strain in partially relaxed annealed specimens was obtained by double-crystal x-ray diffractometry and the corresponding strain phonon shift was measured by Raman scattering spectroscopy. For epilayers grown on Si it was found that the epilayer Si-Si phonon frequency varies linearly with strain. The magnitude of the strain shift coefficient b however showed a small composition dependence varying from b ≈ -700 cm-1 at x = 0 to b ≈ -950 cm-1 at x = 0.35, corresponding to a stress factor τ = 0.40 + 0.57x: + 0.13x2 cm-1/kbar. For the Ge-Ge vibration mode in epilayers grown on Ge, b decreased from ∼-425 cm-1 at x = 1 to ∼-500 cm-1 at x = 0.8, corresponding to a stress factor τ ≈ 0.52 – 0.14x - 0.08x2 cm-1/kbar.

Effects of Se implantation on the compositional disordering of GaAs-AlAs superlattices

1985 ◽  
Vol 56 ◽  
Author(s):  
T. NAKAMURA ◽  
S. KOMIYA ◽  
T. INATA ◽  
S. MUTO ◽  
S. HIYAMIZU
Keyword(s):  
Thermal Diffusion ◽  
Raman Spectra ◽  
Low Dose ◽  
Phonon Frequency ◽  
Gaas Layer ◽  
Probable Mechanism ◽  
Subsequent Annealing ◽  
Alas Layer

AbstractThe LO phonon frequency evaluated from Raman spectra identifies two compositional disordering mechanisms in GaAs-AlAs superlattices. For a high Se dose, the LO phonons of the Al0.5Ga0.5As alloy are observed from the asimplanted samples. That means the compositional disordering occurred just by Se implantation. The probable mechanism for this disordering is the implantation of Ga atoms into the AlAs layer and of Al atoms into the GaAs layer. The superlattices implanted at a low dose are disordered by the subsequent annealing. The mechanism is the enhanced interdiffusion of both Ga and Al atoms between the GaAs and AlAs layers by Se thermal diffusion.

Temperature Dependent Raman Scattering in CsTiOAsO4 Single Crystal

1995 ◽  
Vol 398 ◽  
Author(s):  
A.R. Guo ◽  
C.-S. Tu ◽  
Ruiwu Tao ◽  
R.S. Katiyar ◽  
Ruyan Guo ◽  
...  
Keyword(s):  
Soft Mode ◽  
Low Frequency ◽  
High Mobility ◽  
Vibrational Modes ◽  
Frequency Range ◽  
Temperature Dependent ◽  
Higher Symmetry ◽  
Phonon Spectra ◽  
Symmetry Structure ◽  
Increasing Temperature

ABSTRACTThe longitudinal (LO) and transverse (TO) A1 vibrational modes have been measured between 30-1200 cm−1 as a function of temperature (30–1240 K) for CsTiOAsO4 (CTA). The frequencies for all corresponding Raman components shifted to lower frequencies on increasing the temperature, however, there is no typical soft-mode like behavior observed in the measured frequency range. The relative intensities of the low frequency bands increase dramatically with increasing temperature due to high mobility of Cs+ ion. A higher symmetry structure taking place above 940K has been confirmed by changes in the phonon spectra.

scholarly journals Discovering the forbidden Raman modes at the edges of layered materials

2018 ◽  
Vol 4 (12) ◽  
pp. eaau6252 ◽  
Author(s):  
Yao Guo ◽  
Weixuan Zhang ◽  
Hanchun Wu ◽  
Junfeng Han ◽  
Yongliang Zhang ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Electromagnetic Fields ◽  
Scattered Light ◽  
Layered Materials ◽  
The Body ◽  
Body Region ◽  
Edge Type ◽  
Body Regions ◽  
Raman Modes ◽  
Raman Study

The edges of layered materials have unique properties that substantially differ from the body regions. In this work, we perform a systematic Raman study of the edges of various layered materials (MoS2, WS2, WSe2, PtS2, and black phosphorus). The Raman spectra of the edges feature newly observed forbidden Raman modes, which are originally undetectable from the body region. By selecting the edge type and the polarization directions of the incident and scattered light, all forbidden Raman modes are distinctly detected. Optical simulations show that the edges of layered materials drastically distort the electromagnetic fields of both the incident and scattered light, so that the light interacts with the edges in a distinct way, which differs from its interactions with the body regions.

scholarly journals Manifestation of magnetoelastic interactions in Raman spectra of HoxNd1−xFe3(BO3)4 crystals

2018 ◽  
Vol 08 (02) ◽  
pp. 1850011 ◽  
Author(s):  
A. S. Krylov ◽  
S. N. Sofronova ◽  
I. A. Gudim ◽  
S. N. Krylova ◽  
Rajesh Kumar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Spectra ◽  
Structural Phase Transition ◽  
Solid Solutions ◽  
Order Parameter ◽  
Soft Mode ◽  
Magnetic Phase ◽  
Structural Phase ◽  
Exchange Interactions ◽  
Magnetoelastic Interaction

Raman spectra of Ho[Formula: see text]NdxFe(BO3)4 ([Formula: see text], 0.75, 0.5, 0.25) have been studied in temperature range 10–400[Formula: see text]K. Two compositions ([Formula: see text], [Formula: see text]) demonstrate structural phase transition with soft mode restoration. The addition of Nd atoms increases interatomic spacing and decreases the temperature of structural phase transition. The solid solutions ([Formula: see text], 0.5, 0.25) demonstrate the emergence of the peaks corresponding to magnetoelastic interaction below Néel temperature. The order parameter of the magnetic phase transition has been determined. The equal concentrations of holmium and neodymium atoms prevent magnon soft modes condensation caused by exchange interactions in Fe–O–Fe chains are observed. Calculations confirm the data obtained in the experiment.

RAMAN STUDY OF VANADIUM-DOPED TITANIA NANOPOWDERS SYNTHESIZED BY SOL-GEL METHOD

2010 ◽  
Vol 24 (06n07) ◽  
pp. 667-675 ◽  
Author(s):  
M. ŠĆEPANOVIĆ ◽  
S. AŠKRABIĆ ◽  
M. GRUJIĆ-BROJČIN ◽  
A. GOLUBOVIĆ ◽  
Z. DOHČEVIĆ-MITROVIĆ ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Structural Characteristics ◽  
Anatase Phase ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Gel Method ◽  
Sol Gel Method ◽  
Synthesis Conditions ◽  
Raman Modes ◽  
Doped Titania

Pure titania ( TiO 2) nanopowders and TiO 2 doped with 10 mol % of vanadium ions ( V 3+) are synthesized by sol-gel method. The dependence of structural characteristics of nanopowders on synthesis conditions is investigated by X-ray diffraction and Raman spectroscopy. Very intensive modes observed in Raman spectra of all nanopowders are assigned to anatase phase of TiO 2. Additional Raman modes of extremely low intensity which can be related to the presence of small amount of brookite amorphous phase are observed in pure TiO 2 nanopowders. In V -doped nanopowders anatase was the only TiO 2 phase detected. The variations in duration and heating rate of calcination influence slightly the Raman spectra of pure TiO 2, but have a great impact on Raman modes of anatase, as well as the additional Raman modes related to the presence of vanadium oxides in V -doped samples.

CHARACTERISTIC VIBRATIONAL MODES OF H2O ADSORBED MOLECULARLY AND DISSOCIATIVELY ON TITANIUM OXIDE CLUSTERS

2012 ◽  
Vol 11 (06) ◽  
pp. 1289-1295 ◽  
Author(s):  
HONGBO DU ◽  
ABIR DE SARKAR ◽  
YU JIA ◽  
RUI-QIN ZHANG
Keyword(s):  
Water Molecule ◽  
Raman Spectra ◽  
High Frequency ◽  
Dissociative Adsorption ◽  
Vibrational Modes ◽  
High Frequency Range ◽  
Frequency Range ◽  
Adsorbed State ◽  
The One ◽  
Ir And Raman

To provide useful information on dissociation of water molecule on ( TiO2 )n clusters for experimental verification, we have calculated the infrared (IR) and Raman spectra of three possible states involved, namely molecularly adsorbed state, metastable state and dissociatively adsorbed state, using density functional theory at the B3LYP/6-311G(d) level. We find that the characteristic bands of H2O molecules below 2000 cm-1 in both IR and Raman spectra vanish upon both molecular and dissociative adsorption of H2O . In the high frequency range of 3600–4200 cm-1, the adsorption caused the single IR peak of water to split into two bands, while the dissociation removed the one at lower frequency and blue shifted slightly the higher frequency band. The two Raman peaks of the water molecule in the same high frequency range were slightly blue shifted upon adsorption but the one at lower frequency was removed upon dissociation, while the one at high frequency blue shifted slightly. The intensities of vibrational modes of water in 3600–4200 cm-1 are generally significantly enhanced upon both molecular and dissociative adsorption. Our results show clearly signatures of dissociation of water molecule into hydroxyl radical at the terminal site.

Raman Scattering and Photoluminescence Studies of Zn1-xMnxO Nanowires via Vapor Phase Growth

2005 ◽  
Vol 475-479 ◽  
pp. 3525-3530 ◽  
Author(s):  
Y.Q. Chang ◽  
Yi Zhi Chen ◽  
D.P. Yu ◽  
Z.L. Fang ◽  
G.H. Li ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Raman Spectra ◽  
Vapor Phase ◽  
Phonon Frequency ◽  
Quantum Confinement Effect ◽  
Phase Growth ◽  
Vapor Phase Growth ◽  
Band Emission ◽  
Near Band Emission ◽  
Photoluminescence Studies

In this paper, we investigated the Raman scattering and photoluminescence of Zn1-xMnxO nanowires synthesized by the vapor phase growth. The changes of E2(High) and A1(LO) phonon frequency in Raman spectra indicate that the tensile stress increases while the free carrier concentration decreases with the increase of manganese. The Raman spectra exited by the different lasers exhibit the quantum confinement effect of Zn1-xMnxO nanowires. The photoluminescence spectra reveal that the near band emission is affected by the content of manganese obviously. The values of IUV/G decrease distinctly with the manganese increase also demonstrate that more stress introduced with the more substitution of Mn for Zn.

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