Thermal conductivity inhibition in phonon engineered core-shell cross-section modulated Si/Ge nanowires

Nika, Denis L.; Cocemasov, Alexandr I.; Crismari, Dmitrii V.; Balandin, Alexander A.

doi:10.1063/1.4807389

Cited by 58 publications

(73 citation statements)

References 64 publications

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“…4d), in which the modulation appears more often along the length of the channel, have slightly higher thermal conductance than channels with larger periodicity in which case the modulation appears in larger intervals. The reason is that channels with larger periodicity have larger unit cells, and undergo stronger band-folding, which results in many more narrow gaps in the spectrum in agreement with previous works [19,27,29,51] (although not severely reduced group velocities as seen in Fig. 2).…”

Section: Methodssupporting

confidence: 78%

“…This makes the bands primarily more 'flat' compared to the bands of the uniform channels (either the wide or the narrow ones). As a consequence, a large number of narrow bandgaps appearsc in the phonon spectrum as the length of a region increases, in agreement with previous studies [19,27,29]. Both the appearance of bandgaps and the reduction in the group velocity, lead to reduction in the thermal conductance as we discuss below.…”

Section: Methodssupporting

confidence: 77%

“…However, as explained above, increasing the periodicity of the channel increases the unit cell of the structure and results in a smaller Brillouin zone and enhanced band-folding with a large number of bands [27,53]. Interaction between these different bands results in fragmented spectra with bands of lower group velocities and more narrow bandgaps, which reduce the thermal conductance.…”

Section: Methodsmentioning

confidence: 99%

“…In a more recent work, Blandre et al have considered the amorphisation of the outer surface of diameter modulated Si nanowire channels, which resulted in even lower thermal conductivities [33]. Nika et al have investigated the thermal conductivity of Si/Ge crosssection-modulated nanowires and found a large decrease in the thermal conductivity compared to the bulk material as well [27]. They attributed this to modifications of the phonon spectra in the modulated nanowires which 'reduces the group velocities and introduces localization of certain modes in both the narrow and the wider segments of the nanowire'.…”

Section: Introductionmentioning

confidence: 99%

“…A series of engineering techniques to reduce the thermal conductivity of nanoscale channels (without introducing severe disorder that will also reduce the electronic conductivity) are under investigation, i.e. the use of superlattice or superlattice-like geometries [19][20][21][22], engineering the surface roughness [23][24][25][26], the use of core-shell cross section modulated channels [27,28], twinning superlattice channels [29], channel surface decoration and amorphization techniques, etc.…”

Section: Introductionmentioning

confidence: 99%

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Phonon transport effects in one-dimensional width-modulated graphene nanoribbons

Karamitaheri

Neophytou

2016

Journal of Applied Physics

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We investigate the thermal conductance of one-dimensional periodic widthmodulated graphene nanoribbons using lattice dynamics for the phonon spectrum and the Landauer formalism for phonon transport. We conduct a full investigation considering all relevant geometrical features, i.e. the various lengths and widths of the narrow and wide regions that form the channel. In all cases that we examine, we find that widthmodulation suppresses the thermal conductance at values even up to ~70 % below those of the corresponding uniform narrow nanoribbon. We show that this can be explained by the fact that the phonon spectrum of the width-modulated channels acquires less dispersive bands with lower group velocities and several narrow bandgaps, which reduce the phonon transmission function significantly. The largest degradation in thermal conductance is determined by the geometry of the narrow regions. The geometry of the wider regions also influences thermal conductance, although modestly. Our results add to the ongoing efforts in understanding the details of phonon transport at the nanoscale, and our conclusions are generic and could also apply to other one-dimensional channel materials.

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Section: Methodssupporting

confidence: 78%

Section: Methodssupporting

confidence: 77%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phonon transport effects in one-dimensional width-modulated graphene nanoribbons

Karamitaheri

Neophytou

2016

Journal of Applied Physics

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Quantum‐Confinement‐Enhanced Thermoelectric Properties in Modulation‐Doped GaAs–AlGaAs Core–Shell Nanowires

et al. 2019

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Nanowires (NWs) hold great potential in advanced thermoelectrics due to their reduced dimensions and low‐dimensional electronic character. However, unfavorable links between electrical and thermal conductivity in state‐of‐the‐art unpassivated NWs have, so far, prevented the full exploitation of their distinct advantages. A promising model system for a surface‐passivated one‐dimensional (1D)‐quantum confined NW thermoelectric is developed that enables simultaneously the observation of enhanced thermopower via quantum oscillations in the thermoelectric transport and a strong reduction in thermal conductivity induced by the core–shell heterostructure. High‐mobility modulation‐doped GaAs/AlGaAs core–shell NWs with thin (sub‐40 nm) GaAs NW core channel are employed, where the electrical and thermoelectric transport is characterized on the same exact 1D‐channel. 1D‐sub‐band transport at low temperature is verified by a discrete stepwise increase in the conductance, which coincided with strong oscillations in the corresponding Seebeck voltage that decay with increasing sub‐band number. Peak Seebeck coefficients as high as ≈65–85 µV K−1 are observed for the lowest sub‐bands, resulting in equivalent thermopower of S2σ ≈ 60 µW m−1 K−2 and S2G ≈ 0.06 pW K−2 within a single sub‐band. Remarkably, these core–shell NW heterostructures also exhibit thermal conductivities as low as ≈3 W m−1 K−1, about one order of magnitude lower than state‐of‐the‐art unpassivated GaAs NWs.

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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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Thermal conductivity inhibition in phonon engineered core-shell cross-section modulated Si/Ge nanowires

Cited by 58 publications

References 64 publications

Phonon transport effects in one-dimensional width-modulated graphene nanoribbons

Phonon transport effects in one-dimensional width-modulated graphene nanoribbons

Quantum‐Confinement‐Enhanced Thermoelectric Properties in Modulation‐Doped GaAs–AlGaAs Core–Shell Nanowires

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

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