Anharmonic line shift and linewidth of the Raman mode in covalent semiconductors

Lang, G.; Karch, K.; Schmitt, Michaël; Pavone, P.; Mayer, Andreas; Wehner, R.K.; Strauch, D.

doi:10.1103/physrevb.59.6182

Cited by 92 publications

(51 citation statements)

References 42 publications

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“…For the Raman frequency of diamond, an anharmonic zero-point softening of 20 cm -1 is found [59]. An estimate based on the isotope effect measured for this frequency leads to 16 ± 4 cm -1 [59] whereas an ab initio calculation [60] yields 32 cm -1 . Einstein oscillator fits can also be used to represent the temperature dependence of the long wavelength refractive index n(T) (i.e., in the region of transparency) of crystals.…”

Section: Dependence Of the Refractive Index On Temperature And On Isomentioning

confidence: 99%

Electron–phonon interaction in tetrahedral semiconductors

Cardona

2005

Solid State Communications

161

141

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Considerable progress has been made in recent years in the field of ab initio calculations of electronic band structures of semiconductors and insulators. The oneelectron states (and the concomitant two-particle excitations) have been obtained without adjustable parameters, with a high degree of reliability. Also, more recently, the electron-hole excitation frequencies responsible for optical spectra have been calculated. These calculations, however, are performed with the constituent atoms fixed in their crystallographic positions and thus neglect the effects of the lattice vibrations (i.e. electron-phonon interaction) which can be rather large, even larger than the error bars assumed for ab initio calculations.Effects of electron-phonon interactions on the band structure can be experimentally investigated in detail by measuring the temperature dependence of energy gaps or critical points (van Hove singularities) of the optical excitation spectra. These studies have been complemented in recent years by observing the dependence of such spectra on isotopic mass whenever different stable isotopes of a given atom are available at affordable prices. In crystals composed of different atoms, the effect of the vibration of each separate atom can thus be investigated by isotopic substitution. Because of the zero-point vibrations, such effects are present even at zero temperature (T = 0).In this paper we discuss state-of-the-art calculations of the dielectric function spectra and compare them with experimental results, with emphasis on the differences introduced by the electron-phonon interaction. The temperature dependence of various optical parameters will be described by means of one or two (in a few cases three) Einstein oscillators, except at the lowest temperatures where the T 4 law (contrary to the Varshni T 2 result) will be shown to apply. Increasing an isotopic mass increases the energy gaps, except in the case of monovalent Cu (e.g., CuCl) and possibly Ag (e.g., AgGaS 2 ). It will be shown that the gaps of tetrahedral materials containing an element of the first row of the periodic table (C,N,O) are strongly affected by the electron-phonon interaction. It will be conjectured that this effect is related to the superconductivity recently observed in heavily boron-doped carbon.

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Section: Dependence Of the Refractive Index On Temperature And On Isomentioning

confidence: 99%

Electron–phonon interaction in tetrahedral semiconductors

Cardona

2005

Solid State Communications

161

141

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“…Hence, a detailed non-perturbative treatment of anharmonicity is crucial to understand the lattice-dynamics and thermoelectric efficiency of materials. From a theoretical point of view, several approximations [6][7][8][9] have been developed in the last years to tackle this problem and it is finally becoming possible to describe anharmonic effects beyond the perturbative regime 10,11 .…”

Section: Introductionmentioning

confidence: 99%

Strong anharmonicity in the phonon spectra of PbTe and SnTe from first principles

et al. 2018

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At room temperature, PbTe and SnTe are efficient thermoelectrics with a cubic structure. At low temperature, SnTe undergoes a ferroelectric transition with a critical temperature strongly dependent on the hole concentration, while PbTe is an incipient ferroelectric. By using the stochastic self-consistent harmonic approximation, we investigate the anharmonic phonon spectra and the occurrence of a ferroelectric transition in both systems. We find that vibrational spectra strongly depends on the approximation used for the exchange-correlation kernel in density functional theory. If gradient corrections and the theoretical volume are employed, then the calculation of the free energy Hessian leads to phonon spectra in good agreement with experimental data for both systems. In PbTe, we reproduce the transverse optical mode phonon satellite detected in inelastic neutron scattering and the crossing between the transverse optical and the longitudinal acoustic modes along the ΓX direction. In the case of SnTe, we describe the occurrence of a ferroelectric transition from the high temperature Fm3m structure to the low temperature R3m one.

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“…Phonon dispersions of silicon have been reported, as have phonon densities of states (DOS), thermal properties and mode Grüneisen parameters [12][13][14][15][16][17] . The work with density functional theory (DFT) on silicon includes one of its earliest successes for determining the crystal structure of a solid at elevated temperatures 18 .…”

Section: Introductionmentioning

confidence: 99%

Phonon anharmonicity in silicon from 100 to 1500 K

et al. 2015

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Inelastic neutron scattering was performed on silicon powder to measure the phonon density of states (DOS) from 100 to 1500 K. The mean fractional energy shifts with temperature of the modes were ∆εi/εi∆T = −0.07 giving a mean isobaric Grüneisen parameter of +6.95±0.67, significantly different from the isothermal parameter of +0.98. These large effects are beyond the predictions from quasiharmonic models using density functional theory (DFT) or experimental data, demonstrating large effects from phonon anharmonicity. At 1500 K the anharmonicity contributes 0.15 kB/atom to the vibrational entropy, compared to the 0.03 kB/atom from quasiharmonicity. Excellent agreement was found between the entropy from phonon DOS measurements and the reference JANAF thermodynamic entropy from calorimetric measurements.2

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Anharmonic line shift and linewidth of the Raman mode in covalent semiconductors

Cited by 92 publications

References 42 publications

Electron–phonon interaction in tetrahedral semiconductors

Electron–phonon interaction in tetrahedral semiconductors

Strong anharmonicity in the phonon spectra of PbTe and SnTe from first principles

Phonon anharmonicity in silicon from 100 to 1500 K

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