Vibrational properties of amorphous Si and Ge

Alben, R.; Weaire, D.; Smith, J. E.; Brodsky, M. H.

doi:10.1103/physrevb.11.2271

Cited by 349 publications

(113 citation statements)

References 51 publications

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“…The knowledge of all the eigenmodes allows us to calculate the reduced polarized Raman spectra of the NS4 glass model using the bond polarizability approximation (BPA) [22] presented in details in Refs. [5,23].…”

Section: Vdos and Raman Spectra Calculationsmentioning

confidence: 99%

Vibrational properties of a sodium tetrasilicate glass: Ab initio versus classical force fields

Ispas

Zotov

Wispelaere

et al. 2005

Journal of Non-Crystalline Solids

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We have determined the vibrational properties of a sodium tetrasilicate (Na 2 Si 4 O 9 ) glass model generated by molecular dynamics simulations. The study has been carried out using a classical valence force fields approach as well as an ab initio approach in the framework of the density functional theory. The total and partial vibrational densities of states (VDOS) are presented, as well as some characteristics of the vibrational modes (participation ratios, correlation lengths). For the low-frequency bands below 500 cm −1 , we find that the shapes of the two calculated VDOS as well as those of their corresponding partial VDOS are quite similar. For the intermediate-and high-frequency ranges, we observe larger discrepancies between the two calculations. Using the eigenmodes of the dynamical matrix we also calculate the polarized Raman spectra within the bond-polarizability approximation. We find an overall agreement between the calculated parallel polarized (VV) Raman spectra and the corresponding experimental spectrum. Regarding the perpendicular depolarized (VH) Raman spectrum, the comparison of the calculated spectra to the experimental data indicates a need for an adjustment of the VH bond-polarizability parameters.

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Section: Vdos and Raman Spectra Calculationsmentioning

confidence: 99%

Vibrational properties of a sodium tetrasilicate glass: Ab initio versus classical force fields

Ispas

Zotov

Wispelaere

et al. 2005

Journal of Non-Crystalline Solids

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“…6 On the other hand, by fitting the Raman spectra and the density of vibrational states of a-Si to atomistic models, several authors obtained ␣ / ␤ values in the 2.9-6.7 range. 33,34 With these values, the expression inside the brackets departs from unity by less than 8%. This means that as indicated in the right-hand side of Eq.…”

Section: Microscopic Interpretation Of the Energy Of Relaxation mentioning

confidence: 99%

Quantification of the bond-angle dispersion by Raman spectroscopy and the strain energy of amorphous silicon

Roura¹,

Farjas²,

Cabarrocas³

2008

Journal of Applied Physics

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A thorough critical analysis of the theoretical relationships between the bond-angle dispersion in a-Si,⌬ , and the width of the transverse optical Raman peak, ⌫, is presented. It is shown that the discrepancies between them are drastically reduced when unified definitions for ⌬ and ⌫ are used. This reduced dispersion in the predicted values of ⌬ together with the broad agreement with the scarce direct determinations of ⌬ is then used to analyze the strain energy in partially relaxed pure a-Si. It is concluded that defect annihilation does not contribute appreciably to the reduction of the a-Si energy during structural relaxation. In contrast, it can account for half of the crystallization energy, which can be as low as 7 kJ/mol in defect-free a-Si.

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“…36 For the calculation of the first-order Raman spectra of the models we use the bond polarizability approximation. 36,39,40 Each Raman line is additionally broadened by 15 cm Ϫ1 to account for the additional disorder not present in the computer generated models and their finite size. This broadening was determined by matching the calculated width of the TO Raman line after broadening to the experimental value.…”

Section: A Calculation Proceduresmentioning

confidence: 99%

Structure and physical properties of paracrystalline atomistic models of amorphous silicon

Voyles

Zotov

Nakhmanson

et al. 2001

Journal of Applied Physics

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We have examined the structure and physical properties of paracrystalline molecular dynamics models of amorphous silicon. Simulations from these models show qualitative agreement with the results of recent mesoscale fluctuation electron microscopy experiments on amorphous silicon and germanium. Such agreement is not found in simulations from continuous random network models. The paracrystalline models consist of topologically crystalline grains which are strongly strained and a disordered matrix between them. We present extensive structural and topological characterization of the medium range order present in the paracrystalline models and examine their physical properties, such as the vibrational density of states, Raman spectra, and electron density of states. We show by direct simulation that the ratio of the transverse acoustic mode to transverse optical mode intensities I TA /I TO in the vibrational density of states and the Raman spectrum can provide a measure of medium range order. In general, we conclude that the current paracrystalline models are a good qualitative representation of the paracrystalline structures observed in the experiment and thus provide guidelines toward understanding structure and properties of medium-range-ordered structures of amorphous semiconductors as well as other amorphous materials.

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Vibrational properties of amorphous Si and Ge

Cited by 349 publications

References 51 publications

Vibrational properties of a sodium tetrasilicate glass: Ab initio versus classical force fields

Vibrational properties of a sodium tetrasilicate glass: Ab initio versus classical force fields

Quantification of the bond-angle dispersion by Raman spectroscopy and the strain energy of amorphous silicon

Structure and physical properties of paracrystalline atomistic models of amorphous silicon

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