Randomness-Induced Phonon Localization in Graphene Heat Conduction

Hu, Shiqian; Zhang, Zhongwei; Jiang, Pengfei; Chen, Jie; Volz, Sébastian; Nomura, Masahiro; Li, Baowen

doi:10.1021/acs.jpclett.8b01653

Cited by 121 publications

(87 citation statements)

References 80 publications

(119 reference statements)

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“…To keep pace with the demand of continuous miniaturization of thermoelectric devices, recently much attention has been devoted to the development of 2D high‐efficiency TE materials with controllable thickness. [ 5–7 ] In general, the TE efficiency is characterized by the dimensionless figure of merit ZT = S 2 σT /(κ L + κ e ), where S , σ, T , κ L , and κ e are Seebeck coefficient, electrical conductivity, absolute temperature, lattice thermal conductivity and electronic thermal conductivity, respectively. Apparently, the high TE efficiency can be achieved by increasing the power factor (PF = S 2 σ) together with suppressing the sum of thermal conductivity (κ L + κ e ).…”

Section: Introductionmentioning

confidence: 99%

High ZT 2D Thermoelectrics by Design: Strong Interlayer Vibration and Complete Band‐Extrema Alignment

Zhang

Liu

Tao

et al. 2020

Adv Funct Materials

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The discovery of a record high figure of merit (ZT) of ≈2.6 associated with bulk SnSe has stimulated considerable enthusiasm in searching for 2D systems with similar high ZT. However, previously reported 2D thermoelectric (TE) materials generally possess very low ZT due to the high lattice thermal conductivity (κ L ) and/or small power factor (PF). Herein, a very high ZT (≈2.08) value associated with atomically thin 2D KAgSe nanosheet is reported, which also exhibits an unprecedented low intrinsic κ L (≈0.03 Wm −1 K −1 at 700 K for trilayer) and fairly large PF. The low κ L mainly stems from the high lattice anharmonicity induced by both the "interfacial shear slip" vibrations and the asymmetric "AgSe pair" vibrations from distorted AgSe 4 tetrahedrons. Meanwhile, the complete band-extrema alignment and coexistence of heavy and light bands result in an optimal Seebeck coefficient and electrical conductivity, thereby a large PF. This work suggests not only an alternative way to acquiring high lattice anharmonicity but also a highly competitive 2D TE candidate for wide applications.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.202001200.devices, recently much attention has been devoted to the development of 2D highefficiency TE materials with controllable thickness. [5][6][7] In general, the TE efficiency is characterized by the dimensionless figure of merit ZT = S 2 σT/(κ L + κ e ), where S, σ, T, κ L , and κ e are Seebeck coefficient, electrical conductivity, absolute temperature, lattice thermal conductivity and electronic thermal conductivity, respectively. Apparently, the high TE efficiency can be achieved by increasing the power factor (PF = S 2 σ) together with suppressing the sum of thermal conductivity (κ L + κ e ).Currently, the TE efficiency can be improved by two approaches: i) Tuning effective mass to improve the electronic transport and ii) increasing phonon scattering to suppress the lattice thermal transport. [8][9][10][11] For a given carrier concentration, a large carrier effective mass (m*) contributes to a large S, and the m* is proportional to the band effective mass (m b *) according to m* = N V 2/3 m b *, where N V refers to the band degeneracy. [10,12] A large m b *, however, will reduce the carrier mobility μ since m b 1/ * 2 µ ∝ (2D systems). [13][14][15][16] Hence, to optimize S 2 σ, it is important to attain high N V and moderate m b * simultaneously. A high N V can be achieved either by mixing two types of low-symmetric compounds into a reconstructed highly symmetric structure or by alloying/doping to converge different bands in the Brillouin zone. [8,[17][18][19] For electronic bands at the band edge, a moderate m b * can be realized in principle through element doping or strain engineering. [20] However, in practice, many compounds have limited doping capability and are easily damaged by strain; and the crystal symmetry of the reconstructed structure is uncontrollable. Regarding increasing phonon scattering, intro...

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Section: Introductionmentioning

confidence: 99%

High ZT 2D Thermoelectrics by Design: Strong Interlayer Vibration and Complete Band‐Extrema Alignment

Zhang

Liu

Tao

et al. 2020

Adv Funct Materials

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“…It has also been predicted that reduced thermal conductivity can be achieved by engineering the thermal transport in graphene periodic phononic structures. [15] Furthermore, it has been reported that lateral confinement alone allows to change Nanoscale scanning thermal microscopy (SThM) transport measurements from cryogenic to room temperature on 2D structures with sub 30 nm resolution are reported. This novel cryogenic operation of SThM, extending the temperature range of the sample down to 150 K, yields a clear insight into the nanothermal properties of the 2D nanostructures and supports the model of ballistic transport contribution at the edge of the detached areas of exfoliated graphene which leads to a size-dependent thermal resistance of the detached material.…”

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confidence: 99%

Nanoscale Thermal Transport in 2D Nanostructures from Cryogenic to Room Temperature

Evangeli

Spiece

Sangtarash

et al. 2019

Adv Elect Materials

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2D materials with high in-plane thermal conductivity such as graphene, which is also highly electrically conductive, or hexagonal boron nitride (hBN), which is electrically insulating, have been proposed for heat management applications, [2] whereas MoS 2 has been used as an active channel on electronic devices due to its comparable bandgap to silicon. [3] 2D materials can also be excellent thermal insulators for cross-plane thermal transport, with WSe 2 known to possess one of the lowest thermal conductivity for a continuous solid-state material. [4] Furthermore, vertical, [5] lateral, [6] or composite [7] heterostructures of 2D materials are shown to be potential candidates for electronic applications. These unique properties open new possibilities for the development of highperformance thermoelectric and phase change memory structures.For thermoelectric applications, 2D materials are also highly attractive due to their high Seebeck coefficient values. For example, the Seebeck coefficient of graphene has been reported to be between 10 and 180 µV K −1 [8] while that of MoS 2 can be orders of magnitude higher (3 × 10 5 µV K −1 ). [9] Nevertheless, their implementation in such devices needs clever use of thermal anisotropy of the in-plane [10] and cross-plane [11] thermal conductivities. The efficiency of a thermoelectric device, which converts the waste heat to energy is determined by the dimensionless figure of merit ZT = S 2 σT/k, where S is the Seebeck coefficient, σ is the electrical conductivity, and k = k ph + k el is the thermal conductivity due to electrons (el) and phonons (ph). Therefore, a highly efficient thermoelectric device requires materials with high S and σ and low k in the direction of the electron flow.Recently, it has been proposed that stacking of 2D materials to create heterostructures is an efficient way of enhancing the efficiency of thermoelectric devices. [12] For graphene/MoS 2 stacks, high figure of merit values (up to 2.8) are predicted, due to the reduction of k and heat transport through the sharp edges of MoS 2 nanoribbons. [13] Additionally, the thermal conductivity of rippled graphene was predicted to notably drop compared to flat one [14] leading to more efficient thermoelectrics. It has also been predicted that reduced thermal conductivity can be achieved by engineering the thermal transport in graphene periodic phononic structures. [15] Furthermore, it has been reported that lateral confinement alone allows to change Nanoscale scanning thermal microscopy (SThM) transport measurements from cryogenic to room temperature on 2D structures with sub 30 nm resolution are reported. This novel cryogenic operation of SThM, extending the temperature range of the sample down to 150 K, yields a clear insight into the nanothermal properties of the 2D nanostructures and supports the model of ballistic transport contribution at the edge of the detached areas of exfoliated graphene which leads to a size-dependent thermal resistance of the detached material. The thermal resistance of graph...

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“…Recently, increasing efforts have been made to control the thermal transport [36][37][38]. Analogous to the technique of anti-reflective coating and reflective coating, we can apply the reversion between the half-wave loss and the no-wave loss for the reflected phonon to manipulate the thermal transport across an interface.…”

Section: Discussionmentioning

confidence: 99%

Phonon quarters-wave loss

Xiong

Wang

2019

New J. Phys.

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There has been a growing interest in the phase of phonon, due to the theoretical prediction (Phys. Rev. Lett. 115.11 (2015)) and the experimental observation (Science 359.6379 (2018)) of chiral phonons, which have different phases in different components. While half-wave loss is a well-known concept in optics, in this work, a series of plateaus of quarters-wave loss are first found for the reflected phonon across an interface by using an atomic junction model. These plateaus can be understood by the Smatrix in the system with time-reversal symmetry. If a phonon wave propagates from a low acousticimpedance material (or a low cutoff frequency material) to a higher one in the long-wave limit (or in the high frequency limit), a half-wave loss takes place for the reflected phonon; however, the plateau of half-wave loss for reflected phonon occurs in the whole frequency domain if phonon transfers to a material with a larger spring constant. Besides the half-wave loss, we also observe plateaus of quarterwave (three-quarters-wave) loss in long wave limit when the two leads with identical acoustic impedance are coupled by a weak (strong) coupling in comparison with the optimum thermal coupling. The quarters-wave loss for phonons can be applied to chiral phonon manipulation and other phononics devices.

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Randomness-Induced Phonon Localization in Graphene Heat Conduction

Cited by 121 publications

References 80 publications

High ZT 2D Thermoelectrics by Design: Strong Interlayer Vibration and Complete Band‐Extrema Alignment

High ZT 2D Thermoelectrics by Design: Strong Interlayer Vibration and Complete Band‐Extrema Alignment

Nanoscale Thermal Transport in 2D Nanostructures from Cryogenic to Room Temperature

Phonon quarters-wave loss

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