Thermal conductivity of silicon nanomeshes: Effects of porosity and roughness

Wolf, Stefanie; Neophytou, Neophytos; Kosina, H.

doi:10.1063/1.4879242

Cited by 49 publications

(63 citation statements)

References 34 publications

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“…where λpp is the average phonon mean-free-path (MFP) of Si. In previous work simulations were carried out to compare and validate the simulator for bulk values of silicon thermal conductivity [24,26,41,43]. In particular we have also shown that our simulator results compare very well with several literature simulation and experimental results for the thermal conductivity versus temperature for pristine bulk Si and porous Si cases [25,26].…”

Section: Appendix: Single Phonon Monte Carlo Methodssupporting

confidence: 73%

“…This section gives details about the Monte Carlo approach we employ, its validation, and the assumptions related the scattering term used. Full details can be found in our previous works [24,41] . The simulation process is as follows: The simulation domain of size Lx = 1000 nm × Ly = 500 nm is initialized with a 'Hot' and 'Cold' end, set at TH = 310 K and TC = 290 K respectively.…”

Section: Appendix: Single Phonon Monte Carlo Methodsmentioning

confidence: 99%

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Thermal rectification optimization in nanoporous Si using Monte Carlo simulations

Chakraborty

Brooke

Hulse

et al. 2019

Journal of Applied Physics

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We investigate thermal rectification in nanoporous silicon using a semi-classical Monte Carlo (MC) simulation method. We consider geometrically asymmetric nanoporous structures, and investigate the combined effects of porosity, inter-pore distance, and pore position relative to the device boundaries. Two basis geometries are considered, one in which the pores are arranged in rectangular arrays, and ones in which they form triangular arrangements. We show that systems: i) with denser, compressed pore arrangements (i.e with smaller inter-pore distances), ii) with pores positioned closer to the device edge/contact, and iii) with pores in a triangular arrangement, can achieve rectification of over 55%. Introducing smaller pores into existing porous geometries in a hierarchical fashion increases rectification even further to over 60%. Importantly, for the structures we simulate, we show that sharp rectifying junctions, separating regions of long from short phonon mean-free-paths are more beneficial for rectification than spreading the asymmetry throughout the material along the heat direction in a graded fashion.

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Section: Appendix: Single Phonon Monte Carlo Methodssupporting

confidence: 73%

Section: Appendix: Single Phonon Monte Carlo Methodsmentioning

confidence: 99%

Thermal rectification optimization in nanoporous Si using Monte Carlo simulations

Chakraborty

Brooke

Hulse

et al. 2019

Journal of Applied Physics

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“…Monte Carlo simulations for phonons in Si nanomeshes in the diffusive phonon transport limit, and compared the calculated thermal conductivity with experimental data [64]. In general, the experimental measurements showed lower conductivity compared to the semiclassical result, in some cases significantly lower, which demonstrates that indeed coherent effects could be strong.…”

Section: Thermoelectric Properties Of Bulk-size Nanostructured Simentioning

confidence: 99%

Prospects of low-dimensional and nanostructured silicon-based thermoelectric materials: findings from theory and simulation

Neophytou

2015

Eur. Phys. J. B

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Original citation: Neophytou, Neophytos. (2015) Prospects of low-dimensional and nanostructured siliconbased thermoelectric materials : findings from theory and simulation. The European Physical Journal B, 88 (4). Permanent WRAP url:http://wrap.warwick.ac.uk/77435 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:"The final publication is available at Springer via http://dx.doi.org/10.1140/epjb/e2015-50673-9 " A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. AbstractSilicon based low-dimensional materials receive significant attention as new generation thermoelectric materials after they have demonstrated record low thermal conductivities. Very few works to-date, however, report significant advances with regards to the power factor. In this review we examine possibilities of power factor enhancement in: i) low-dimensional Si channels and ii) nanocrystalline Si materials. For low-D channels we use atomistic simulations and consider ultra-narrow Si nanowires and ultra-thin Si layers of feature sizes below 15nm. Room temperature is exclusively considered. We show that, in general, low-dimensionality does not offer possibilities for power factor improvement, because although the Seebeck coefficient could slightly increase, the conductivity inevitably degrades at a much larger extend. The power factor in these channels, however, can be optimized by proper choice of geometrical parameters such as the transport orientation, confinement orientation, and confinement length scale. Our simulations show that in the case where room temperature thermal conductivities as low as κl=2 W/mK are achieved, the ZT figure of merit of an optimized Si lowdimensional channel could reach values around unity. For the second case of materials, we show that by making effective use of energy filtering, and taking advantage of the inhomogeneity within the nanocrystalline geometry, the underlying potential profile and dopant distribution, large improvements in the thermoelectric power factor can be achieved. The paper is intended...

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“…These are molecular dynamics (MD) [18][19][20][21][22], the Boltzmann Transport Equation (BTE) for phonons using scattering rates based on the single mode relaxation time approximation (SMRTA) [23][24][25][26], the non-equilibrium Green's function (NEGF) method [27][28][29][30][31][32][33], and the Landauer method [34][35][36], and even more simplified semi-analytical methods based on the Casimir formula to describe boundary scattering [37,38].…”

Section: Introductionmentioning

confidence: 99%

Phonon transport simulations in low-dimensional, disordered graphene nanoribbons

Neophytou¹,

Karamitaheri²

2015

2015 IEEE 15th International Conference on Nanotechnology (IEEE-NANO)

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Thermal conductivity of silicon nanomeshes: Effects of porosity and roughness

Cited by 49 publications

References 34 publications

Thermal rectification optimization in nanoporous Si using Monte Carlo simulations

Thermal rectification optimization in nanoporous Si using Monte Carlo simulations

Prospects of low-dimensional and nanostructured silicon-based thermoelectric materials: findings from theory and simulation

Phonon transport simulations in low-dimensional, disordered graphene nanoribbons

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