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Vibrational properties and phonon anharmonicity in ZnS1-xSex: Inelastic neutron scattering, Raman scattering, X-ray diffraction measurements and lattice dynamical studies

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Title Vibrational properties and phonon anharmonicity in ZnS1-xSex: Inelastic neutron scattering, Raman scattering, X-ray diffraction measurements and lattice dynamical studies
 
Creator BASAK, T
RAO, M
CHAPLOT, SL
SALKE, N
RAO, R
DHANASEKARAN, R
RAJARAJAN, AK
ROLS, S
MITTAL, R
JAYAKRISHNAN, VB
SASTRY, PU
 
Subject Lattice dynamics
Semiconductors
Phonons
Raman spectra
OPTICAL PHONONS
MIXED-CRYSTALS
ZINC CHALCOGENIDES
ALLOYS
PRESSURE
SEMICONDUCTORS
DISPERSION
ZNSXSE1-X
TEMPERATURE
DEPENDENCE
 
Description Inelastic neutron scattering, Raman and X-ray diffraction measurements coupled with lattice dynamical calculations (employing a semi empirical transferable potential model) have been carried out to gain a detailed understanding of the peculiar vibrational spectrum exhibited by the mixed crystal ZnS1-xSex. Raman scattering measurements performed over a varying range of temperature (100-800 K) and pressure (up to 13 GPa) have confirmed that the additional mode observed in the spectra are visible over the entire range of temperature and pressure. Correlation of the individual motions of atoms (obtained from computed total and partial phonon density of states) with the inelastic neutron scattering measurements (carried out over the entire Brillouin zone) have then indicated that the existence of the additional mode in ZnS1-xSex is due to the vibrations of the Se atom being in resonance with that of the Saturn. Further, it has been shown that the presence of this additional mode can be tuned by varying the mass of the atom at the Se site. In addition, an analysis of bond length distribution with increasing Se concentration have elucidated that bond length spread is not responsible for the presence of the additional mode. An analysis of the peak shifts of the Raman modes with temperature and pressure indicate that the anharmonicity of the vibrational modes increases with increasing compositional disorder. This is attributed to the fact that increasing Se concentration gives rise to a distribution of bondlengths in ZnS1-xSex which is responsible for this compositional disorder induced anharmonicity. Our computations have thus revealed that mass of the anion is responsible for the presence of additional mode while bond-length distribution gives rise to the existence of compositional disorder induced anharmonicity in ZnS1-xSex. Further, it is observed that the contribution of explicit anharmonicity to the total anharmonicity becomes dominant at higher temperatures. This compound also exhibits negative thermal expansion at low temperatures as obtained from our X-ray diffraction measurements as a function of temperature (10-800 K). (C) 2013 Elsevier B.V. All rights reserved.
 
Publisher ELSEVIER SCIENCE BV
 
Date 2014-12-28T16:27:11Z
2014-12-28T16:27:11Z
2014
 
Type Article
 
Identifier PHYSICA B-CONDENSED MATTER, 433149-156
0921-4526
1873-2135
http://dx.doi.org/10.1010/j.physb.2013.10.036
http://dspace.library.iitb.ac.in/jspui/handle/100/16882
 
Language English