Thermal conductivity of silicon bulk and nanowires: Effects of isotopic composition, phonon confinement, and surface roughness

Kazan, M.; Guisbiers, Grégory; Pereira, S.; Correia, M. R.; Masri, P.; Bruyant, Aurélien; Volz, Sébastian; Royer, Pascal

doi:10.1063/1.3340973

Cited by 102 publications

(70 citation statements)

References 81 publications

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“…However, a comprehensive understanding of the physical mechanisms underlying so large TC reduction is lacking. The effect of surface roughness and surface disorder on phonons has been so far interpreted in terms of phonon scattering [26][27][28][29][30], but scattering would not account for mean free path reduction of long-wavelength low-frequency modes. Recent theoretical work demonstrated that surface nanostructures, such as nanopillars at the surface of thin films or nanowires, can efficiently reduce TC through resonances, a mechanism that is intrinsically different from scattering [31,32].…”

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confidence: 99%

Native surface oxide turns alloyed silicon membranes into nanophononic metamaterials with ultralow thermal conductivity

et al. 2017

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A detailed understanding of the relation between microscopic structure and phonon propagation at the nanoscale is essential to design materials with desired phononic and thermal properties. Here we uncover a new mechanism of phonon interaction in surface oxidized membranes, i.e., native oxide layers interact with phonons in ultra-thin silicon membranes through local resonances. The local resonances reduce the low frequency phonon group velocities and shorten their mean free path. This effect opens up a new strategy for ultralow thermal conductivity design as it complements the scattering mechanism which scatters higher frequency modes effectively. The combination of native oxide layer and alloying with germanium in concentration as small as 5% reduces the thermal conductivity of silicon membranes to 100 time lower than the bulk. In addition, the resonance mechanism produced by native oxide surface layers is particularly effective for thermal condutivity reduction even at very low temperatures, at which only low frequency modes are populated.Controlling terahertz vibrations and heat transport in nanostructures has a broad impact on several applications, such as thermal management in micro-and nano-electronics, renewable energies harvesting, sensing, biomedical imaging and information and communication technologies [1][2][3][4][5][6][7][8]. Significant efforts have been made to understand and engineer heat transport in nanoscale silicon due to its natural abundance and technological relevance [9][10][11][12]. In the past decade researchers explored strategies to obtain silicon based materials with low thermal conductivity (TC) and unaltered electronic transport coefficients, so to achieve high thermoelectric figure of merit and enable silicon-based thermoelectric technology [11][12][13][14][15][16][17][18].From the earlier studies it was recognized that lowdimensional silicon nanostructures, such as nanowires, thin films and nano membranes feature a largely reduced TC, up to 50 times lower than that of bulk at room temperature. TC reduction becomes more prominent with the reduction of the characteristic dimension of the nanostructures [19][20][21][22]. Theory and experiments consistently show that surface disorder and the presence of disordered material at surfaces play a major role in determining the TC of nanostructures [12,[23][24][25]. However, a comprehensive understanding of the physical mechanisms underlying so large TC reduction is lacking. The effect of surface roughness and surface disorder on phonons has been so far interpreted in terms of phonon scattering [26][27][28][29][30], but scattering would not account for mean free path reduction of long-wavelength low-frequency modes. Recent theoretical work demonstrated that surface nanostructures, such as nanopillars at the surface of thin films or nanowires, can efficiently reduce TC through resonances, a mechanism that is intrinsically different from scattering [31,32]. Surface resonances alter directly phonon dispersion relations by hybridizing with prop...

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confidence: 99%

Native surface oxide turns alloyed silicon membranes into nanophononic metamaterials with ultralow thermal conductivity

et al. 2017

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“…The cutoff frequency is the only parameter that relies on nanowire measurements [34]. Following the procedure at [34,41] a very good description of NW thermal conductivity can be obtained without the need to compute the full dispersions by introducing an adjustable parameter, the cutoff frequency or the Debye temperature. So, the Debye temperature is taken into account as a free adjustable parameter with permitted values below the bulk value.…”

Section: Theorymentioning

confidence: 99%

“…The constant parameters used in the calculations are listed in Table 1. Using an adjustable parameter, which is usual in the literature [41][42][43][44], attempts were made to use the three parameters, θ , γ and P , as adjustable parameters to correlate the calculated LTC to that of the corresponding experimental data at [21]. The values of θ , γ and P were adjusted such that the best fit for calculated LTC to the experimental data was obtained.…”

Section: Theorymentioning

confidence: 99%

Phonon Scatterings in the Lattice Thermal Conductivity of Si_(1-x) Ge_x Alloy Nanowires: Theoretical Study

Mamand¹

2014

NANO

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Theoretical investigation of the alloy concentration and temperature dependences of the lattice thermal conductivity of silicon-germanium nanowires is performed using the Steigmeier and Abeles model. Phonon scattering processes are represented by frequency-dependent relaxation time approximation. In addition to the commonly considered acoustic three-phonon umklapp processes, phonon-boundary and point-defect scattering mechanisms are assumed. No distinction is made between longitudinal and transverse phonons. The importance of all the mechanisms involved in the model is clearly demonstrated. Analysis of the results shows that: (1) alloy scattering is the dominant scattering mechanism at intermediate and high temperatures; (2) thermal conductivity is mainly depends on the alloy concentration across the full range of temperatures; (3) weak diameter dependence of thermal conductivity is observed in Si 1 x Ge x alloy nanowires; (4) the roughness of nanowires depends on the alloy concentration and has a major role in decreasing thermal conductivity at low temperatures; (5) the anharmonicity parameter is not size-dependent, as compared to Si and Ge nanowires. These findings provide new insights into the fundamental understanding of high-performance nanostructural semiconductors of relevance to optoelectronic and thermoelectric devices.

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“…However, the use of silicon isotopes has aroused interest due to various applications. The removal of the 29 Si and 30 Si isotopes increases the thermal conductivity because of the reduction of the defects in the crystalline network [1,2]. On the other hand, there is a growing interest in obtaining highly enriched 28 Si on account of its up-and-coming applications in quantum computing.…”

Section: Introductionmentioning

confidence: 99%

Silicon Isotope Separation by two frequency IRMPD

Risaro¹,

D'Accurso²,

Codina³

et al. 2017

Opt. Pura Apl.

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ABSTRACT:InfraRed Multi-Photon Dissociation (IRMPD) is a highly selective laser isotope separation technique. This process consists of a sequential IR photon absorption from the ground vibrational state up to dissociation by a molecule that contains the isotope of interest. High dissociation threshold molecules require large intensity radiation fields. This drawback could be overcome by two-frequency IRMPD. In this technique, a low energy laser resonant with the first energy levels guarantees isotopic selectivity excitation and a second non-resonant large energy laser achieves molecular dissociation. The possibility of obtaining silicon laser isotopic enrichment using SiF4 as working molecule was investigated in this work. Two-frequency IRMPD of SiF4 with two TEA CO2 single transverse mode lasers was studied in a molecular jet. The dissociation process was monitored with a Time-of-Flight mass spectrometer with UV multi-photon ionization. The excitation laser fluence and wavelength dependence of the isotopic dissociation estimator, α, and the enrichment factor estimator, β, were determined and compared to those obtained in single-frequency IRMPD.Key words: isotope separation, laser, silicon, infrared multiphoton dissociation. RESUMEN:La Disociación Multifotónica InfrarRoja (DMFIR) es un método de separación de isótopos con láser altamente selectivo el cual consiste en la absorción secuencial de fotones resonantes con un modo de vibración de la molécula que contiene el isótopo de interés, desde el estado fundamental hasta sobrepasar el umbral de disociación. Las moléculas con umbrales de disociación alto requieren láseres de alta energía. Esta desventaja puede superarse mediante la DMFIR con dos frecuencias. En esta técnica, un láser de baja energía, resonante con los primeros niveles vibracionales garantiza la selectividad isotópica del proceso y otro, menos restrictivo en sintonía, pero de alta fluencia produce la disociación molecular. En este trabajo se investigó la posibilidad de obtener enriquecimiento isotópico utilizando SiF4 como molécula de trabajo. Se estudió la DMFIR de SiF4 con dos frecuencias provenientes de dos láseres de CO2 TEA monomodo transversal en un jet molecular. Como sistema de detección se utilizó un espectrómetro de masas de tiempo de vuelo con ionización multifotónica UV. Se determinó el efecto de la variación de la fluencia y longitud de onda de los láseres de excitación y de disociación sobre los valores de los estimadores α y β asociados a la eficiencia de la disociación y al grado de enriquecimiento isotópico obtenido, respectivamente, y se comparó con los resultados obtenidos en la DMFIR con una sola frecuencia.Palabras clave: separación de isótopos, láser, silicio, disociación multifotónica infrarroja. 413-415 (1997).https://doi.org/10. 1080/18811248.1997.9733683 [12] A. Yokoyama, H. Ohba, M. Hashimoto, K. Katsumata, H. Akagi, T. Ishii, A. Ohya, S. Arai, "Silicon isotope separation utilizing infrared multiphoton dissociation of Si2F6 irradiated with two-frequency CO2 laser ligh...

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Thermal conductivity of silicon bulk and nanowires: Effects of isotopic composition, phonon confinement, and surface roughness

Cited by 102 publications

References 81 publications

Native surface oxide turns alloyed silicon membranes into nanophononic metamaterials with ultralow thermal conductivity

Native surface oxide turns alloyed silicon membranes into nanophononic metamaterials with ultralow thermal conductivity

Phonon Scatterings in the Lattice Thermal Conductivity of Si_(1-x) Ge_x Alloy Nanowires: Theoretical Study

Silicon Isotope Separation by two frequency IRMPD

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