Vibrational spectrum of amorphous silicon: Experiment and computer simulation

Kamitakahara, W. A.; Soukoulis, C. M.; Shanks, H. R.; Buchenau, U.; Grest, Gary S.

doi:10.1103/physrevb.36.6539

Cited by 119 publications

(66 citation statements)

References 12 publications

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“…This confirms by direct simulation that the I TA /I TO intensity ratio in the VDOS can be a sensitive probe of the degree of MRO. Of the models considered, only PC-K1 has a I TA /I TO ratio close to the experimental value of 0.88 obtained from inelastic neutron scattering experiments, 8 which agrees with the variable coherence microscopy simulations presented in Sec. III B.…”

Section: B Vibrational Modessupporting

confidence: 76%

“…9, is similar in all the PC models and is in good agreement with experimental neutron scattering measurements. 7,8 The calculated VDOS also compares well with previous VDOS calculations for a-Si models constructed by different methods using various potentials. 36,[41][42][43][44][45][46] As in crystalline Si, the peak at ϳ175 cm Ϫ1 is commonly assigned to transverse acoustic ͑TA͒-like vibrations, the weak peak at ϳ325 cm Ϫ1 to longitudinal acoustic ͑LA͒-like vibrations, the weak shoulder at ϳ400 cm Ϫ1 to longitudinal optic ͑LO͒-like vibrations, and the high-frequency peak at ϳ500 cm Ϫ1 to transverse optic ͑TO͒-like vibrations.…”

Section: B Vibrational Modessupporting

confidence: 66%

“…These glimpses come from the first sharp diffraction peak, 4 more local probes of the material like nuclear magnetic resonance 5 and near-edge x-ray absorption fine structure, 6 and especially probes of the vibrational spectrum such as neutron scattering 7,8 and Raman spectroscopy. 9,10 Unfortunately, interpreting these measurements in terms of a specific sample structure has proven elusive.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: B Vibrational Modessupporting

confidence: 76%

Section: B Vibrational Modessupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

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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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“…1. They show the usual shape of VDOS obtained for amorphous silicon [27], with a first peak related to acoustic transverse modes and a second well defined peak at high frequencies that is reminiscent of optic modes in the crystal ( Fig. 1(a)).…”

Section: Density Of Statesmentioning

confidence: 58%

Boson peak and Ioffe-Regel criterion in amorphous siliconlike materials: The effect of bond directionality

et al. 2016

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The vibrational properties of model amorphous materials are studied by combining complete analysis of the vibration modes, dynamical structure factor and energy diffusivity with exact diagonalization of the dynamical matrix and the Kernel Polynomial Method which allows a study of very large system sizes. Different materials are studied that differ only by the bending rigidity of the interactions in a Stillinger-Weber modelization used to describe amorphous silicon. The local bending rigidity can thus be used as a control parameter, to tune the sound velocity together with local bonds directionality. It is shown that for all the systems studied, the upper limit of the Boson peak corresponds to the Ioffe-Regel criterion for transverse waves, as well as to a minimum of the diffusivity. The Boson peak is followed by a diffusivity's increase supported by longitudinal phonons. The Ioffe-Regel criterion for transverse waves corresponds to a common characteristic mean-free path of 5-7Å (which is slightly bigger for longitudinal phonons), while the fine structure of the vibrational density of states is shown to be sensitive to the local bending rigidity.

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“…U ac ZPE can be calculated from the experimental density of vibrational states, g i ͑ ͒, of a-Si and c-Si, 43 U ac…”

Section: Appendix: Relation Between U Ac and Q Acmentioning

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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Vibrational spectrum of amorphous silicon: Experiment and computer simulation

Cited by 119 publications

References 12 publications

Structure and physical properties of paracrystalline atomistic models of amorphous silicon

Structure and physical properties of paracrystalline atomistic models of amorphous silicon

Boson peak and Ioffe-Regel criterion in amorphous siliconlike materials: The effect of bond directionality

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

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