Thermal conductivity of germanium crystals with different isotopic compositions

Asen-Palmer, M.; Bartkowski, K.; Gmelin, E.; Cardona, M.; Zhernov, A. P.; Inyushkin, A. V.; Талденков, А. Н.; Ozhogin, V. I.; Itoh, Kohei M.; Häller, E. E.

doi:10.1103/physrevb.56.9431

Cited by 387 publications

(339 citation statements)

References 68 publications

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“…While at these temperatures the thermal conductivity of the 28 Si sample investigated at the Kurchatov Institute and at the IChHPS RAS coincides with that of nat Si, the thermal conductivities of the MPI FKF 28 Si sample are by about a factor of 2 larger 5 than those of nat Si. We ascribe this difference to additional phonon scattering by chemical impurities or different surface scattering due to different sample surface finishing [7]. We finally discuss the thermal radiation losses which around room temperature may provide an additional channel for heat dissipation in samples with a small cross section.…”

Section: Resultsmentioning

confidence: 99%

Thermal conductivity of isotopically enriched 28Si: revisited

Kremer

Gräf

Cardona

et al. 2004

Solid State Communications

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114

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The thermal conductivity of isotopically enriched 28 Si (enrichment better than 99.9%) was redetermined independently in three laboratories by high precision experiments on a total of 4 samples of different shape and degree of isotope enrichment in the range from 5 to 300 K with particular emphasis on the range near room temperature. The results obtained in the different laboratories are in good agreement with each other. They indicate that at room temperature the thermal conductivity of isotopically enriched 28 Si exceeds the thermal conductivity of Si with a natural, unmodified isotope mixture by 10±2 %. This finding is in disagreement with an earlier report by Ruf et al. At ∼26 K the thermal conductivity of 28 Si reaches a maximum. The maximum value depends on sample shape and the degree of isotope enrichment and exceeds the thermal conductivity of natural Si by a factor of ∼8 for a 99.982% 28 Si enriched sample. The thermal conductivity of Si with natural isotope composition is consistently found to be ∼3% lower than the values recommended in the literature. PACS: 66.70.+f, 63.20.Mt, 74.25.Fy, 65.40.Ba, 65.90.+i Keywords: silicon, stable isotopes, thermal conductivity INTRODUCTIONPhonon scattering due to the presence of different isotopes in an otherwise pure crystal (no chemical defects or dislocations) has been identified as a mechanism that strongly affects the thermal conductivity κ [1−3]. The availability of larger quantities of highly isotope-enriched materials recently revived the interest in this effect in order to study the mechanisms underlying the thermal conductivity and possibly to improve material properties [4−8].Recently, the observation of a significantly enhanced thermal conductivity of isotopically enriched 28 Si near room temperature by Capinski [9] and Ruf et al. [10] has generated large interest. In these studies, it was found that the thermal conductivity of isotopically enriched 28 Si is enhanced by about 60% over that of silicon with natural isotopic composition. This rather high isotope effect attracted considerable attention concerning both, fundamental physics and applications. For technical applications, a significantly enlarged thermal conductivity at room 2 temperature would be of interest for high performance electronic devices. [11]. From the fundamental physics aspect, the experimental results were unexpected since the observed isotopic effect was significantly larger than the prediction of simple theoretical estimates [10−13] and more advanced model calculations [14]. On the other hand, theoretical papers [15−17] were published with the results supporting the data of refs. [9,10]. A large isotopic effect at room temperature is in principle only possible if normal phonon-phonon scattering processes play an important role in determining the formation of the non-equilibrium distribution function of phonons at these temperatures.The large room temperature isotope effect was questioned following the results of an experimental study by Gusev et al. [18] which indicate that th...

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Section: Resultsmentioning

confidence: 99%

Thermal conductivity of isotopically enriched 28Si: revisited

Kremer

Gräf

Cardona

et al. 2004

Solid State Communications

Self Cite

114

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“…An analytical model, taking into account the perturbed phonon population caused by normal process, was proposed initially by Callaway 153 and widely adopted in the study the κ L for solids over the years. 147,154,155 The resistive scattering processes include grain boundary scattering (τ B ), point defect scattering (τ PD ), phonon-phonon Umklapp processes (τ U ), electron-phonon interaction (τ e-p ), etc. The overall scattering rate is obtained by adding scattering rates of the individual scattering processes,…”

Section: From the Conventional Phonon-phonon Interactions To Nanostrumentioning

confidence: 99%

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

et al. 2016

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During the last two decades, we have witnessed great progress in research on thermoelectrics. There are two primary focuses. One is the fundamental understanding of electrical and thermal transport, enabled by the interplay of theory and experiment; the other is the substantial enhancement of the performance of various thermoelectric materials, through synergistic optimisation of those intercorrelated transport parameters. Here we review some of the successful strategies for tuning electrical and thermal transport. For electrical transport, we start from the classical but still very active strategy of tuning band degeneracy (or band convergence), then discuss the engineering of carrier scattering, and finally address the concept of conduction channels and conductive networks that emerge in complex thermoelectric materials. For thermal transport, we summarise the approaches for studying thermal transport based on phonon-phonon interactions valid for conventional solids, as well as some quantitative efforts for nanostructures. We also discuss the thermal transport in complex materials with chemical-bond hierarchy, in which a portion of the atoms (or subunits) are weakly bonded to the rest of the structure, leading to an intrinsic manifestation of part-crystalline part-liquid state at elevated temperatures. In this review, we provide a summary of achievements made in recent studies of thermoelectric transport properties, and demonstrate how they have led to improvements in thermoelectric performance by the integration of modern theory and experiment, and point out some challenges and possible directions. INTRODUCTION Thermoelectric (TE) materials are materials that can generate useful electric potentials when subjected to a temperature gradient (known as the Seebeck effect). Conversely, they also transfer heat against the temperature gradient when a current is driven against this potential (known as the Peltier effect). They are promising energy materials with many applications, such as waste heat harvesting, radioisotope TE power generation, and solid state Peltier refrigeration, all of which are driving growing research interest. A key challenge is to improve the TE properties in order to obtain more efficient energy conversion and in turn enable new practical applications. Good TE materials must have excellent electrical transport properties, measured by the TE power factor ( = S 2 σ, where S is the Seebeck coefficient and σ is the electrical conductivity), and also a very low thermal conductivity κ (composed of the electronic contribution κ e , the lattice contribution κ L , and the bipolar contribution κ bi ). Combining the two aspects gives us the dimensionless figure of merit ZT,

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“…This is true even for common materials such as silicon and germanium. 1 A tremendous simplification is achieved in the calculation of ͑i͒ in bulk semiconductors 4,5 and nanomaterials 6 by using the relaxation time approximation to solve the PBE. However, the relaxation time approximation is derived under the assumption of elastic scattering, but the anharmonic phonon-phonon scattering is an inelastic scattering process.…”

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confidence: 99%

Intrinsic lattice thermal conductivity of semiconductors from first principles

Broido

Malorny

Birner

et al. 2007

Applied Physics Letters

862

733

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We present an ab initio theoretical approach to accurately describe phonon thermal transport in semiconductors and insulators free of adjustable parameters. This technique combines a Boltzmann formalism with density functional calculations of harmonic and anharmonic interatomic force constants. Without any fitting parameters, we obtain excellent agreement ͑Ͻ5% difference at room temperature͒ between the calculated and measured intrinsic lattice thermal conductivities of silicon and germanium. As such, this method may provide predictive theoretical guidance to experimental thermal transport studies of bulk and nanomaterials as well as facilitating the design of new materials.

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Thermal conductivity of germanium crystals with different isotopic compositions

Cited by 387 publications

References 68 publications

Thermal conductivity of isotopically enriched 28Si: revisited

Thermal conductivity of isotopically enriched 28Si: revisited

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

Intrinsic lattice thermal conductivity of semiconductors from first principles

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