Lattice dynamics and thermoelectric properties of nanocrystalline silicon–germanium alloys

Claudio, Tania; Stein, Niklas; Petermann, Nils; Stroppa, Daniel G.; Koza, Michael Marek; Wiggers, Hartmut; Klobes, Benedikt; Schierning, Gabi; Hermann, Raphaël P.

doi:10.1002/pssa.201532500

Cited by 8 publications

(5 citation statements)

References 39 publications

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“…The lattice constant of bulk Si is determined to be 5.50 Å, which agrees well with the theoretical result of 5.48 Å [ 30 ] and the experimental result of 5.43 Å [ 31 ]. As compared with bulk Si, the lattice constant of bulk Ge is larger, i.e., 5.71 Å, which is consistent with the calculated result of 5.65 Å [ 30 ] and the experimental value of 5.77 Å [ 31 ]. Our calculated threshold displacement energies for bulk Si and Ge are summarized in Table 1 , along with the associated defects after the displacement events.…”

Section: Resultssupporting

confidence: 86%

A Theoretical Simulation of the Radiation Responses of Si, Ge, and Si/Ge Superlattice to Low-Energy Irradiation

et al. 2018

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In this study, the low-energy radiation responses of Si, Ge, and Si/Ge superlattice are investigated by an ab initio molecular dynamics method and the origins of their different radiation behaviors are explored. It is found that the radiation resistance of the Ge atoms that are around the interface of Si/Ge superlattice is comparable to bulk Ge, whereas the Si atoms around the interface are more difficult to be displaced than the bulk Si, showing enhanced radiation tolerance as compared with the bulk Si. The mechanisms for defect generation in the bulk and superlattice structures show somewhat different character, and the associated defects in the superlattice are more complex. Defect formation and migration calculations show that in the superlattice structure, the point defects are more difficult to form and the vacancies are less mobile. The enhanced radiation tolerance of the Si/Ge superlattice will benefit for its applications as electronic and optoelectronic devices under radiation environment.

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Section: Resultssupporting

confidence: 86%

A Theoretical Simulation of the Radiation Responses of Si, Ge, and Si/Ge Superlattice to Low-Energy Irradiation

et al. 2018

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“…Other processing techniques such as high pressure torsion [45], hot deformation [46], and liquid phase sintering [47] may be optimized to maximize the amount of internal-strain in the material. The softening effects in Si and Si-Ge alloys by Caudio et al [36,48], and in Bi 2 Te 3 and Sb 2 Te 3 based materials by Klobes et al…”

Section: Engineering Thermal Conductivity Through Lattice Softeningmentioning

confidence: 99%

Lattice Softening Significantly Reduces Thermal Conductivity and Leads to High Thermoelectric Efficiency

et al. 2019

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The influence of micro/nanostructure on thermal conductivity is a topic of great scientific interest and of particular technological importance to thermoelectrics. The current understanding is that structural defects primarily decrease thermal conductivity through phonon scattering where the phonon dispersion and speed of sound are fixed when describing thermal transport, especially when chemical composition is unchanged. Experimental work on a PbTe model system is presented which shows that the speed of sound linearly decreases with increased internal-strain. This softening of the materials lattice completely accounts for the reduction in lattice thermal conductivity, without the introduction of additional phonon scattering mechanisms. Additionally, we show that a major contribution to the reduction in thermal conductivity, and the resulting improvement in thermoelectric figure of merit (zT > 2), in high efficiency Na-doped PbTe can be attributed to this internal-strain induced lattice softening effect. While inhomogeneous internal-strain fields are known to introduce phonon scattering centers, this study demonstrates that internal-strain can also soften a materials lattice on average, modifying the speeds of sound and phonon dispersion. This presents new avenues to control lattice thermal conductivity, beyond phonon scattering, with microstructural defects and internal-strain. In practice, many engineering materials will exhibit both softening and scattering effects, as is shown in silicon. This work shines new light on studies of thermal conductivity in fields of energy materials, microelectronics, and nano-scale heat transfer.

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“…It is observed that the nanocomposite samples exhibit low thermal conductivity as compared to the coarse-grained alloy . Claudio et al measured the density of phonon states using inelastic neutron scattering and concluded that nanostructuring causes an increase in the density of phonon states by enhancing the point defect scattering . The decrease in the thermal conductivity is more pronounced in a transition-metal-doped alloy, which can be attributed to the difference in bond anharmonicities leading to bond heterogeneity in the alloy .…”

Section: Total and Lattice Thermal Conductivity Of Si080ge0184ni0016 ...mentioning

confidence: 99%

“…57 Claudio et al measured the density of phonon states using inelastic neutron scattering and concluded that nanostructuring causes an increase in the density of phonon states by enhancing the point defect scattering. 58 The decrease in the thermal conductivity is more pronounced in a transition-metal-doped alloy, which can be attributed to the difference in bond anharmonicities leading to bond heterogeneity in the alloy. 59 Furthermore, the reduction in Cr-doped alloy can be endorsed to the presence of additional unpaired electrons in Cr to attain half-filled stability of 3d orbitals, which enhances the electron− phonon scattering.…”

mentioning

confidence: 99%

Potency of Extended X-ray Absorption Fine Structure Spectroscopy toward the Determination of Individual Bond Grüneisen Parameter for High Thermoelectric Performance

Basu

Nayak

Kumar

et al. 2023

ACS Appl. Energy Mater.

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Si–Ge is a well-known disordered alloy exhibiting high anharmonicity. These two features, disorder and anharmonicity, arise due to the unique nature of bonding instead of structural complexity and are beneficial as they limit the thermal conduction and are widely used in high-temperature thermoelectric applications. In this regard, a comprehensive understanding of the nature of interatomic bonds and the calculation of the Grüneisen parameter, which is a characteristic metric of anharmonicity, of the individual bond are essential to design a crystalline solid along with the development of a high-throughput thermoelectric alloy exhibiting ultralow lattice thermal conductivity. Here, we demonstrate the origin of the low lattice thermal conductivity, κl, of ∼0.8 and 0.4 Wm–1 K–1 for the transition-metal (Ni and Cr)-doped Si–Ge alloy, respectively, due to the difference in the anharmonic pair potential achieved using synchrotron-based X-ray absorption fine structure spectroscopy. The technique enables the determination of the Grüneisen parameter of the individual bond in the alloy and thus reveals the unpaired electron-induced bond anharmonicities and bonding heterogeneity. The technique also determines the bond Grüneisen parameter more precisely in comparison to the values obtained from the speed of sound, as the latter neglects the existence of the soft TO mode, which also contributes to lattice dynamics. Thus, the synergistic presence of (i) heteroatoms as point scatters (mass contrast), (ii) bonding anharmonicities, and (iii) electron–phonon scattering suppresses the lattice thermal conductivity beyond the theoretical alloy limit. Furthermore, the analysis imparts a conception for the estimation of the bond Grüneisen parameter through the acquisition and analysis of extended X-ray analysis of fine structure (EXAFS) spectra.

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Lattice dynamics and thermoelectric properties of nanocrystalline silicon–germanium alloys

Cited by 8 publications

References 39 publications

A Theoretical Simulation of the Radiation Responses of Si, Ge, and Si/Ge Superlattice to Low-Energy Irradiation

A Theoretical Simulation of the Radiation Responses of Si, Ge, and Si/Ge Superlattice to Low-Energy Irradiation

Lattice Softening Significantly Reduces Thermal Conductivity and Leads to High Thermoelectric Efficiency

Potency of Extended X-ray Absorption Fine Structure Spectroscopy toward the Determination of Individual Bond Grüneisen Parameter for High Thermoelectric Performance

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