Manipulating phonons at the nanoscale: Impurities and boundaries

Zardo, Ilaria; Rurali, Riccardo

doi:10.1016/j.cogsc.2018.12.006

Cited by 10 publications

(7 citation statements)

References 96 publications

(78 reference statements)

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“…The manipulation of phonons and the dynamical tuning of the thermal conductivity of a solid are problems of fundamental interest in condensed matter physics [1][2][3] and have important implications in renewable energy applications -such as vibrational energy harvesting [4], thermoelectricity [5] or electrocaloric cooling [6]-and for the implementation of a phonon-based logic, which relies on thermal diodes [7,8] and transistors [9], and where information is transmitted and processed by heat carriers.…”

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confidence: 99%

Giant Electrophononic Response in PbTiO3 by Strain Engineering

2019

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We demonstrate theoretically how, by imposing epitaxial strain in a ferroelectric perovskite, it is possible to achieve a dynamical control of phonon propagation by means of external electric fields, which yields a giant electrophononic response, i.e. the dependence of the lattice thermal conductivity on external electric fields. Specifically, we study the strain-induced manipulation of the lattice structure and analyze its interplay with the electrophononic response. We show that tensile biaxial strain can drive the system to a regime where the electrical polarization can be effortlessly rotated and thus yield giant electrophononic responses that are at least one order of magnitude larger than in the unstrained system. These results derive directly from the almost divergent behavior of the electrical susceptibility at those critical strains that drive the polarization on the verge of a spontaneous rotation. PACS numbers:1 Heat in insulators and semiconductors is carried by phonons, the quanta of lattice vibrations, and the thermal conductivity is determined by the associated dissipative processes. The manipulation of phonons and the dynamical tuning of the thermal conductivity of a solid are problems of fundamental interest in condensed matter physics [1-3] and have important implications in renewable energy applications -such as vibrational energy harvesting [4], thermoelectricity [5] or electrocaloric cooling [6]-and for the implementation of a phonon-based logic, which relies on thermal diodes [7, 8] and transistors [9], and where information is transmitted and processed by heat carriers.Ferroelectric materials favor a spontaneous lattice distortion, below a critical temperature, which has an associated dipole moment that can be controlled with an external electric field. Therefore, they are the ideal playground to explore phonon manipulation, because the modifications of the lattice structure translate directly into changes of the vibrational properties and thus of the thermal conductivity. The polarization, P, can be selectively oriented, for instance, creating neighboring regions separated by domain walls, which may act as phonon scatterers or filters [10,11]. More generally, an electric field can strengthen or weaken P, when it is parallel to it, or partially rotate it, when it has a component perpendicular to it [12][13][14]. This electrophononic effect, whereby an electric field is used to tune the thermal conductivity via a controlled modification of the crystal lattice, paves the way toward an all-electrical control of the heat flux.The temperature-and field-dependent thermal conductivity, κ, can be written as a second-order expansion in terms of the thermal-response tensors α and β aswhere i, j, k, and l are the spatial directions x, y, and z and κ 0 is the conductivity at zero applied field. The physical mechanisms that lead to a coupling between E and κ are different for fields parallel or perpendicular to P. As shown in Ref. 12 by some of us, in the former case the applied field results in a harde...

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Giant Electrophononic Response in PbTiO3 by Strain Engineering

2019

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“…designed nanocomposite SiGe-TiO 2 materials with superior thermoelectric properties due to TiO 2 inclusions with coherent interfaces and modulation dopant regions of boron 10 . This finding of the intentional doping as a new design of thermoelectric devices has some implications on a study performed by Zardo and Rurali using the strategy of varying impurity concentrations to tune the amount of phonon scattering events 11 . The evidence for the fact that the scattering of phonons by nano-scale grains and nanotwins in InSb samples can straightforwardly be related to their thermoelectric behaviour came from the work of Mao et al .…”

Section: Introductionmentioning

confidence: 82%

Enhancing the Seebeck effect in Ge/Si through the combination of interfacial design features

Nadtochiy

Kuryliuk

Strelchuk

et al. 2019

Sci Rep

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Due to their inherent physical properties, thin-film Si/SiGe heterostructures have specific thermal management applications in advanced integrated circuits and this in turn is essential not only to prevent a high local temperature and overheat inside the circuit, but also generate electricity through the Seebeck effect. Here, we were able to enhance the Seebeck effect in the germanium composite quantum dots (CQDs) embedded in silicon by increasing the number of thin silicon layers inside the dot (multi-fold CQD material). The Seebeck effect in the CQD structures and multi-layer boron atomic layer-doped SiGe epitaxial films was studied experimentally at temperatures in the range from 50 to 300 K and detailed calculations for the Seebeck coefficient employing different scattering mechanisms were made. Our results show that the Seebeck coefficient is enhanced up to ≈40% in a 3-fold CQD material with respect to 2-fold Ge/Si CQDs. This enhancement was precisely modeled by taking into account the scattering of phonons by inner boundaries and the carrier filtering by the CQD inclusions. Our model is also able to reproduce the observed temperature dependence of the Seebeck coefficient in the B atomic layer-doped SiGe fairly well. We expect that the phonon scattering techniques developed here could significantly improve the thermoelectric performance of Ge/Si materials through further optimization of the layer stacks inside the quantum dot and of the dopant concentrations.

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“…1 with the yellow to green color scheme). A scaling factor (W = 4×10 5 ) is also introduced to scale the number of phonons simulated to the real population of phonons from 6×10 10 μm -3 that are present at 300 K for computational efficiency [41].…”

Section: Appendix: Single Phonon Monte Carlo Methodsmentioning

confidence: 99%

“…Recently, significant research has been done on understanding and controlling phonon transport in nanostructures for novel materials and applications [1][2][3][4][5][6][7][8]. Since initial findings of thermal rectification between Cu and Cu2O [9] interfaces in the 1930s, various experimental [10][11][12] and theoretical [13][14][15][16][17][18][19][20][21] studies have investigated thermal rectification in different materials.…”

Section: Introductionmentioning

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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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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Manipulating phonons at the nanoscale: Impurities and boundaries

Cited by 10 publications

References 96 publications

Giant Electrophononic Response in PbTiO3 by Strain Engineering

Giant Electrophononic Response in PbTiO3 by Strain Engineering

Enhancing the Seebeck effect in Ge/Si through the combination of interfacial design features

Thermal rectification optimization in nanoporous Si using Monte Carlo simulations

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