Phonon Conduction in Silicon Nanobeam Labyrinths

Park, Woosung; Romano, Giuseppe; Ahn, Chang-Nam; Kodama, Takashi; Park, Joonsuk; Barako, Michael T.; Sohn, Joon; Kim, Soo Jin; Cho, Jungwan; Marconnet, Amy; Asheghi, Mehdi; Kolpak, Alexie M.; Goodson, Kenneth E.

doi:10.1038/s41598-017-06479-3

Cited by 32 publications

(26 citation statements)

References 39 publications

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“…These regions have an increased thermal resistance compared to the average resistance of the other segments of the material, something referred to as reduced 'line-of-sight'. 91,92,93 It is not clear though, how rearrangement of the thermal resistance along the length of the material in low and high resistance regions can affect the thermal conductivity and at what degree. In a previous work, for pores of constant diameter positioned randomly, we have shown that there is indeed a correlation between such rearrangements and lowering thermal conductivity.…”

Section: Analytical Models -Extensions and Validationmentioning

confidence: 99%

Monte Carlo phonon transport simulations in hierarchically disordered silicon nanostructures

2018

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Hierarchical material nanostructuring is considered to be a very promising direction for high performance thermoelectric materials. In this work we investigate thermal transport in hierarchically nanostructured silicon. We consider the combined presence of nanocrystallinity and nanopores, arranged under both ordered and randomized positions and sizes, by solving the Boltzmann transport equation using the Monte Carlo method. We show that nanocrystalline boundaries degrade the thermal conductivity more drastically when the average grain size becomes smaller than the average phonon mean-free-path. The introduction of pores degrades the thermal conductivity even further. Its effect, however, is significantly more severe when the pore sizes and positions are randomized, as randomization results in regions of higher porosity along the phonon transport direction, which introduce significant thermal resistance. We show that randomization acts as a large increase in the overall effective porosity. Using our simulations, we show that existing compact nanocrystalline and nanoporous theoretical models describe thermal conductivity accurately under uniform nanostructured conditions, but overestimate it in randomized geometries. We propose extensions to these models that accurately predict the thermal conductivity of randomized nanoporous materials based solely on a few geometrical features. Finally, we show that the new compact models introduced can be used within Matthiessen's rule to combine scattering from different geometrical features within ~10% accuracy. . 3.7 Wm −1 K −1 for an average pore size of ~ 30 nm and grain sizes between 50 and 80 nm. 21 By reducing both pore and grain sizes, however, Basu et al. reported κ = 1.2 Wm −1 K −1 at 40% porosity in p-type silicon. 22 A recent work in SiGe nanomeshes, reported ultralow κ of 0.55 ± 0.10 Wm −1 K −1 for SiGe nanocrystalline nanoporous structures, a value well below the amorphous limit. 23 A significant amount of work can be found in the literature attempting to clarify these experimental observations. However, theoretical investigations of thermal conductivity in highly/hierarchically disordered nanostructures (which include not only crystalline boundaries, but also pores of random sizes placed at random positions) are very limited. Understanding the qualitative and quantitative details of such geometries on the thermal conductivity would allow the design of more efficient thermoelectrics and heat management materials in general. In this work, we solve the Boltzmann transport equation for phonons in disordered Si nanostructures using the Monte Carlo (MC) method. Monte Carlo, which can capture the details of geometry with relative accuracy, is widely employed to understand phonon transport in various nanostructures such as nanowires, 24,25,26 thin films, 27,28 nanoporous materials, 29,30,31,32,33 polycrystalline materials, 10,15,34,35,36 nanocomposites, 37,38 corrugated structures, 39,40,41,42 silicon-on-insulator devices, 43 etc. We consider geometries that include grai...

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Section: Analytical Models -Extensions and Validationmentioning

confidence: 99%

Monte Carlo phonon transport simulations in hierarchically disordered silicon nanostructures

2018

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“…On one hand, a stronger reduction was measured in silicon with pores (>50%) [9,18,19], nanodots (>70%) [13,68], polycrystalline grains (>80%) [15,69,70], dopants (>50%) [71,72] or germanium atoms (>70%) [14,71,73]. On the other hand, the 20% reduction by the pillars [63] is comparable to the reduction by holes (20–25%) [21,74] or slits (20–30%) [75] covering the same relative area. This relative comparison shows that pillars could achieve the same reduction in the thermal conductivity without sacrificing the material volume or introducing scattering points inside the bulk of the material.…”

Section: Experimental Measurements Of the Thermal Propertiesmentioning

confidence: 99%

Phonon and heat transport control using pillar-based phononic crystals

Anufriev

Nomura

2018

Science and Technology of Advanced Materials

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Phononic crystals have been studied for the past decades as a tool to control the propagation of acoustic and mechanical waves. Recently, researchers proposed that nanosized phononic crystals can also control heat conduction and improve the thermoelectric efficiency of silicon by phonon dispersion engineering. In this review, we focus on recent theoretical and experimental advances in phonon and thermal transport engineering using pillar-based phononic crystals. First, we explain the principles of the phonon dispersion engineering and summarize early proof-of-concept experiments. Next, we review recent simulations of thermal transport in pillar-based phononic crystals and seek to uncover the origin of the observed reduction in the thermal conductivity. Finally, we discuss first experimental attempts to observe the predicted thermal conductivity reduction and suggest the directions for future research.

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“…[36,37,42,43,80] Subsequently, phonon thermal conductivity has been studied in various nm-sc nWVGs morphologies both theoretically and experimentally. [81][82][83] . Experimental observations have in most cases been interpreted quantitatively in terms of scattering effects.…”

Section: Evolution Of Researchmentioning

confidence: 99%

Thermoelectric Metamaterials: Nano‐Waveguides for Thermoelectric Energy Conversion and Heat Management at the Nanoscale

Zianni

2021

Adv Elect Materials

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are heterostructures, electronic and phononic superlattices that have been extensively studied since their discovery nearly 100 years ago. [2][3][4][5][6][7][8][9] Electrons and phonons in geometry-modulated nanostructures, nano-waveguides (nWVGs), have attracted extended research interest since the 1980s. [10][11][12][13][14] In 2010, we proposed nWVGs for thermoelectric efficiency enhancement by geometrical control of electron and phonon properties. [15][16][17] Thermoelectric (TE) energy conversion could ideally serve the need of our society for low-cost green energy production, reduction of CO 2 emissions and waste-heat recycling. Low efficiencies of traditional thermoelectric materials prohibited for long widespread thermoelectric applications. In the last 20 years, the efforts of the thermoelectric community concentrated to alternative approaches, such as using low-dimensional and nanostructured materials, to enhance the TE efficiency. Much progress has been achieved and research is continuing along these lines. Currently, another dimension has been added by that thermoelectric materials could power the Internet of things (IoT). [18] Already-achieved record efficiencies should be sufficient for this purpose. Nevertheless, traditional thermoelectric materials are not suitable for integration into the microelectronics industrial processes. Novel strategies to enhance the TE efficiency of technologically important materials are of predominant importance and interest. Thermoelectric metamaterials (THEMMs), nWVGs with enhanced TE properties, can contribute to this task. Their operation is based on the same principles as low-dimensional and nanostructured materials.The discovery of low-dimensional materials revolutionized science and technology provide the fascinating ability to engineer the energy bandstructure and properties of matter with superlattices of different materials. [19][20][21] Superlattices made of low-dimensional constituent materials exhibited improved properties and novel functionalities due to quantum confinement. Shrinking dimensions to the nanoscale and forming low-dimensional nanostructures and nanocomposite materials opened-up new horizons in science and led to the era of nanotechnology.Low-dimensional materials have one or more dimensions small enough (typically in the nanometric range) so that carriers The idea of using metamaterials for thermoelectrics was proposed 10 years ago. Enhanced thermoelectric effects and decreased thermal conduction are theoretically demonstrated due to modification of electrons and phonons by quantum interference between propagating and scattered waves at geometrical discontinuities. These structures are now considered promising for breakthrough in thermoelectric energy conversion and heat management at the nanoscale. They could ideally power the Internet of things. This review is devoted to electron and phonon transport properties of thermoelectric metamaterials in the quantum confinement regime. Enhanced thermoelectric effects and decreased thermal conductiv...

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Phonon Conduction in Silicon Nanobeam Labyrinths

Cited by 32 publications

References 39 publications

Monte Carlo phonon transport simulations in hierarchically disordered silicon nanostructures

Monte Carlo phonon transport simulations in hierarchically disordered silicon nanostructures

Phonon and heat transport control using pillar-based phononic crystals

Thermoelectric Metamaterials: Nano‐Waveguides for Thermoelectric Energy Conversion and Heat Management at the Nanoscale

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