Phonon Dispersion Relations in Ge at 80 °K

Nilsson, G.; Nelin, G.

doi:10.1103/physrevb.3.364

Cited by 283 publications

(73 citation statements)

References 23 publications

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“…Our results for Si and C agree well with experiment [36] and other theoretical [37,38] results. Note that we have no experimental data to compare with our results for Si 1−x C x alloys.…”

Section: Phonons Dispersionsupporting

confidence: 82%

See 1 more Smart Citation

Density Functional Study of the Carbon Dependence of the Structural, Mechanic, Thermodynamic, and Dynamic Properties of SiC Alloys

Langueur

Kassali

2017

Int J Thermophys

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Using a density functional scheme, for the first time the carbon dependence on the structural, dynamic, thermodynamic, and dynamic properties of Si 1−x C x alloys (x = 0.0 to 1.0 in steps of 0.125) has been investigated. The structural properties of these materials, in particular, the composition dependence of the lattice parameter and bulk modulus, are in excellent agreement with experimental data and follow a quadratic law in (x). A nonlinear relationship is found between the elastic constants C 11 , C 12 , and C 44 and the carbon concentration (x). The behavior of the acoustical and optical phonon frequencies at high-symmetry points Γ , X , and L is predicted. Through the quasi-harmonic Debye model, in which the photonic effects are taken into account, the Debye temperature, the heat capacity, the Helmholtz free energy, the internal energy, and the entropy are determined for the Si 1−x C x compounds.

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“…Our results for Si and C agree well with experiment [36] and other theoretical [37,38] results. Note that we have no experimental data to compare with our results for Si 1−x C x alloys.…”

Section: Phonons Dispersionsupporting

confidence: 82%

“…[37] c Ref. [38] virtual crystal approximation. Phonon band structures of Si 1−x C x have been calculated for 0 < x < 1 in steps of 0.125 of the alloy (x).…”

Section: Phonons Dispersionmentioning

confidence: 99%

Density Functional Study of the Carbon Dependence of the Structural, Mechanic, Thermodynamic, and Dynamic Properties of SiC Alloys

Langueur

Kassali

2017

Int J Thermophys

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“…In VFF model, we take into account two-, three-and four-particle interactions: stretching, bending, stretching-stretching, stretching-bending and bending-bending. All force constants were obtained from the best fit to experimental dispersion for bulk Si [49] and Ge [50]. The calculations of the phonon thermal conductivities κ NW ph and κ…”

mentioning

confidence: 99%

Thermal conductivity inhibition in phonon engineered core-shell cross-section modulated Si/Ge nanowires

Nika

Cocemasov

Crismari

et al. 2013

Applied Physics Letters

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We have shown theoretically that a combination of cross-section modulation and acoustic mismatch in the core-shell Si/Ge nanowires can lead to a drastic reduction of the thermal conductivity. Our calculations, which utilized two different models -five-parameter Bornvon Karman and six-parameter valence-force field -for the lattice vibrations, indicate that the room temperature thermal conductivity of Si/Ge cross-section modulated nanowires is almost three orders of magnitude lower than that of bulk Si. Thermal flux in the modulated nanowires is suppressed by an order of magnitude in comparison with generic Si nanowires.The effect is explained by modification of the phonon spectra in modulated nanowires leading to decrease of the phonon group velocities and localization of certain phonon modes in narrow or wide nanowire segments. The thermal conductivity inhibition is achieved in nanowires without additional surface roughness and, thus, potentially reducing degradation of the electron transport. Our results suggest that the acoustically mismatched cross-section modulated nanowires are promising candidates for thermoelectric applications.

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“…This value is significantly larger than the value of ∼360-374 K that has been measured for the Debye temperature of bulk Ge(111). 37,38 Additionally, RHEED measurements give an effective surface Debye temperature of 96 K for clean c(2 × 8)-Ge(111) surfaces, which was proposed to be due to the weakening of the harmonic force constant of the interlayer potential. 39 Therefore, instead of producing a softer Ge(111) surface, methyl termination imposes a greater rigidity, as indicated by a nearly doubled Debye temperature for the surface.…”

Section: A Vibrational Dynamicsmentioning

confidence: 99%

Vibrational dynamics and band structure of methyl-terminated Ge(111)

Hund

Nihill

Campi

et al. 2015

The Journal of Chemical Physics

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Articles you may be interested inThe interaction of organic adsorbate vibrations with substrate lattice waves in methyl-Si (111) A combined synthesis, experiment, and theory approach, using elastic and inelastic helium atom scattering along with ab initio density functional perturbation theory, has been used to investigate the vibrational dynamics and band structure of a recently synthesized organic-functionalized semiconductor interface. Specifically, the thermal properties and lattice dynamics of the underlying Ge (111) semiconductor crystal in the presence of a commensurate (1 × 1) methyl adlayer were defined for atomically flat methylated Ge (111) surfaces. The mean-square atomic displacements were evaluated by analysis of the thermal attenuation of the elastic He diffraction intensities using the Debye-Waller model, revealing an interface with hybrid characteristics. The methyl adlayer vibrational modes are coupled with the Ge(111) substrate, resulting in significantly softer in-plane motion relative to rigid motion in the surface normal. Inelastic helium time-of-flight measurements revealed the excitations of the Rayleigh wave across the surface Brillouin zone, and such measurements were in agreement with the dispersion curves that were produced using density functional perturbation theory. The dispersion relations for H-Ge(111) indicated that a deviation in energy and lineshape for the Rayleigh wave was present along the nearest-neighbor direction. The effects of mass loading, as determined by calculations for CD 3 -Ge(111), as well as by force constants, were less significant than the hybridization between the Rayleigh wave and methyl adlayer librations. The presence of mutually similar hybridization effects for CH 3 -Ge(111) and CH 3 -Si(111) surfaces extends the understanding of the relationship between the vibrational dynamics and the band structure of various semiconductor surfaces that have been functionalized with organic overlayers. C 2015 AIP Publishing LLC.[http://dx

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Phonon Dispersion Relations in Ge at 80 °K

Cited by 283 publications

References 23 publications

Density Functional Study of the Carbon Dependence of the Structural, Mechanic, Thermodynamic, and Dynamic Properties of SiC Alloys

Density Functional Study of the Carbon Dependence of the Structural, Mechanic, Thermodynamic, and Dynamic Properties of SiC Alloys

Thermal conductivity inhibition in phonon engineered core-shell cross-section modulated Si/Ge nanowires

Vibrational dynamics and band structure of methyl-terminated Ge(111)

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