Thermal Conductivity of Nanocrystalline Silicon: Importance of Grain Size and Frequency-Dependent Mean Free Paths

Wang, Zhaojie; Alaniz, J.E.; Jang, Wanyoung; Garay, Javier E.; Dames, Chris

doi:10.1021/nl1045395

Cited by 410 publications

(410 citation statements)

References 42 publications

Supporting

Mentioning

380

Contrasting

Unclassified

Order By: Relevance

“…However, the experimentally observed 20% reduction in thermal conductivity is interesting to compare with the reduction obtained in other silicon-based nanostructures. 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.…”

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

View full text Add to dashboard Cite

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.

show abstract

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

View full text Add to dashboard Cite

show abstract

“…24,25 We use spherical grains for computational efficiency, but the grain shape can be arbitrary. To calculate the mean free path of each phonon mode, we randomly sample three quantities.…”

mentioning

confidence: 99%

Nanostructure thermal conductivity prediction by Monte Carlo sampling of phonon free paths

McGaughey¹,

Jain²

2012

Applied Physics Letters

View full text Add to dashboard Cite

We propose a method by which the thermal conductivity of a nanostructure with arbitrary geometry can be predicted through Monte Carlo sampling of the free paths associated with phonon-phonon and phonon-boundary scattering. The required inputs are the nanostructure geometry and the bulk phonon frequencies, group velocities, and mean free paths. The method is applied to a thin film in the in-plane and cross-plane directions and to a polycrystalline bulk material. For the film, a faster approach to the bulk thermal conductivity is found compared to predictions made using the Matthiessen rule with the bulk mean free path and an average phonon-boundary scattering length. As the dimensions of electronic, optoelectronic, and energy conversion devices are reduced, the thermal conductivities of the device components (e.g., thin films and nanowires) are also reduced. 1-11 The large electrical power densities in such devices cause Joule heating and the reduced thermal conductivities can lead to high operating temperatures, sub-optimal performance, and poor reliability. Predicting the thermal conductivity reduction in nanostructures is thus a critical part of developing next-generation thermal management strategies.We focus here on semiconducting and insulating nanostructures, where phonons (quantized lattice vibrations) dominate thermal transport. 12 As a nanostructure gets smaller, its thermal conductivity is reduced due to more frequent scattering between phonons and the system boundaries. 1-11 For very small systems (e.g., silicon films thinner than 20 nm), changes in the phonon density of states also affect thermal transport. 2,6,8 Our interest here is nanostructures large enough that the phonon density of states is bulk-like.The thermal conductivity, k, of a nanostructure in the n direction can be predicted from, 12

show abstract

“…The theoretical lines were calculated using a Born-von Karman dispersion model including frequency-dependent expressions for grain-boundary scattering. 31) In this model, κ lat can be expressed as:…”

Section: Resultsmentioning

confidence: 99%

Role of Nanoscale Precipitates for Enhancement of Thermoelectric Properties of Heavily P-Doped Si-Ge Alloys

et al. 2016

View full text Add to dashboard Cite

Thermoelectric (TE) devices can save energy by generating electricity from waste heat. For industrial application of TE power generation, TE materials with high conversion ef ciency and that are non-toxic and inexpensive are required. The nanostructured silicon-germanium (SiGe) alloy is one possible candidate for such TE materials. Nanostructuring is an effective way to improve the conversion ef ciency of materials because it dramatically reduces the lattice thermal conductivity (κ lat ). Here, we experimentally demonstrate effective phonon blocking without carrier mobility deterioration in bulk Si-Ge alloys containing phosphorous-rich nanoscale precipitates connected coherently or semi-coherently with the matrix phase. When the Ge content was less than 5%, the nanoscale precipitates effectively scattered heat-carrying phonons, leading to a suf cient reduction in κ lat . However, at higher Ge content compositions, phonon scattering by Ge substitution with Si was more predominant than phonon scattering by nanoscale precipitates for the reduction of κ lat . As a result, signi cant enhancement of zT was achieved at low Ge contents.

show abstract

Thermal Conductivity of Nanocrystalline Silicon: Importance of Grain Size and Frequency-Dependent Mean Free Paths

Cited by 410 publications

References 42 publications

Phonon and heat transport control using pillar-based phononic crystals

Phonon and heat transport control using pillar-based phononic crystals

Nanostructure thermal conductivity prediction by Monte Carlo sampling of phonon free paths

Role of Nanoscale Precipitates for Enhancement of Thermoelectric Properties of Heavily P-Doped Si-Ge Alloys

Contact Info

Product

Resources

About