Coherent phonon transport in short-period two-dimensional superlattices of graphene and boron nitride

Silva, Carlos Fernandes da; Saiz, Fernan; Romero, David A.; Amón, Cristina H.

doi:10.1103/physrevb.93.125427

Cited by 35 publications

(17 citation statements)

References 47 publications

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“…The observation of a minimum thermal conductivity for a specific superlattice period, as found in our simulations, has been reported by Jiang et al . 46 , Zhu and Ertekin 47 , da Silva et al 48 . and Chen et al .…”

Section: Resultsmentioning

confidence: 99%

Thermal Conductivity of Graphene-hBN Superlattice Ribbons

Felix

Pereira

2018

Sci Rep

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Superlattices are ideal model systems for the realization and understanding of coherent (wave-like) and incoherent (particle-like) phonon thermal transport. Single layer heterostructures of graphene and hexagonal boron nitride have been produced recently with sharp edges and controlled domain sizes. In this study we employ nonequilibrium molecular dynamics simulations to investigate the thermal conductivity of superlattice nanoribbons with equal-sized domains of graphene and hexagonal boron nitride. We analyze the dependence of the conductivity with the domain sizes, and with the total length of the ribbons. We determine that the thermal conductivity reaches a minimum value of 89 W m−1K−1 for ribbons with a superlattice period of 3.43 nm. The effective phonon mean free path is also determined and shows a minimum value of 32 nm for the same superlattice period. Our results also reveal that a crossover from coherent to incoherent phonon transport is present at room temperature for BNC nanoribbons, as the superlattice period becomes comparable to the phonon coherence length. Analyzing phonon populations relative to the smallest superlattice period, we attribute the minimum thermal conductivity to a reduction in the population of flexural phonons when the superlattice period equals 3.43 nm. The ability to manipulate thermal conductivity using superlattice-based two-dimensional materials, such as graphene-hBN nanoribbons, opens up opportunities for application in future nanostructured thermoelectric devices.

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Section: Resultsmentioning

confidence: 99%

Thermal Conductivity of Graphene-hBN Superlattice Ribbons

Felix

Pereira

2018

Sci Rep

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“…Several works on thermal transport in SLs reported a minimum in κ SL as a function of d SL that denotes a crossover from coherent transport (wavelike) at short d SL to incoherent transport (particlelike) at larger d SL . 5,7,13,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] We are not aware of a systematic study of the dependence of κ SL on both d SL and L in these per-vious works. Furthermore, a range of different interpretations for the existence or absence of a minimum have been posed.…”

Section: Discussion and Modeling: Coherent Vs Incoherent Effectsmentioning

confidence: 99%

Interplay between total thickness and period thickness in the phonon thermal conductivity of superlattices from the nanoscale to the microscale: Coherent versus incoherent phonon transport

et al. 2018

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We report on the room temperature thermal conductivity of AlAs-GaAs superlattices (SLs), in which we systematically vary the period thickness and total thickness between 2 − 24 nm and 20.1 − 2,160 nm, respectively. The thermal conductivity increases with the SL thickness and plateaus at a thickness around 200 nm, showing a clear transition from a quasi-ballistic to a diffusive phonon transport regime. These results demonstrate the existence of classical size effects in SLs, even at the highest interface density samples. We use harmonic Atomistic Green's function calculations to capture incoherence in phonon transport by averaging the calculated transmission over several purely coherent simulations of independent SL with different random mixing at the AlAs-GaAs interfaces. These simulations demonstrate the significant contribution of incoherent phonon transport through the decrease in the transmission and conductance in the SLs as the number of interfaces increases. In spite of this conductance decrease, our simulations show a quasilinear increase in thermal conductivity with the superlattice thickness. This suggests that the observation of a quasilinear increase in thermal conductivity can have important contributions from incoherent phonon transport. Furthermore, this seemingly linear slope in thermal conductivity vs. SL thickness data may actually be non-linear when extended to a larger number of periods, which is a signature of incoherent effects. Indeed, this trend for superlattices with interatomic mixing at the interfaces could easily be interpreted as linear when the number of periods is small. Our results reveal that the change in thermal conductivity with period thickness is dominated by incoherent (particlelike) phonons, whose properties are not dictated by changes in the AlAs or GaAs phonon dispersion relations. This work demonstrates the importance of studying both period and sample thickness dependencies of thermal conductivity to understand the relative contributions of coherent and incoherent phonon transport in the thermal conductivity in SLs.

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“…On the other hand, phonon lifetimes and mode contributions are accessible utilizing the spectral-energy-density (SED) method, which considers all anharmonic effects as well [37]. Although SED method is widely used in studying 2D materials and their heterostructures [38][39][40][41][42], the investigation of TMDs based on SED is limited [33,43]. Furthermore, most of the previous reports are restricted to optical modes at the point or along the high-symmetry paths.…”

Section: Introductionmentioning

confidence: 99%

Temperature-dependent phonon spectrum of transition metal dichalcogenides calculated from the spectral energy density: Lattice thermal conductivity as an application

et al. 2019

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Predicting the mechanical and thermal properties of quasi-two-dimensional (2D) transition metal dichalcogenides (TMDs) is an essential task necessary for their implementation in device applications. Although rigorous density-functional-theory-based calculations are able to predict mechanical and electronic properties, mostly they are limited to zero temperature. Classical molecular dynamics facilitates the investigation of temperaturedependent properties, but its performance highly depends on the potential used for defining interactions between the atoms. In this study, we calculated temperature-dependent phonon properties of single-layer TMDs, namely, MoS 2 , MoSe 2 , WS 2 , and WSe 2 , by utilizing Stillinger-Weber-type potentials with optimized sets of parameters with respect to the first-principles results. The phonon lifetimes and contribution of each phonon mode in thermal conductivities in these monolayer crystals are systematically investigated by means of the spectralenergy-density method based on molecular dynamics simulations. The obtained results from this approach are in good agreement with previously available results from the Green-Kubo method. Moreover, detailed analysis of lattice thermal conductivity, including temperature-dependent mode decomposition through the entire Brillouin zone, shed more light on the thermal properties of these 2D crystals. The LA and TA acoustic branches contribute most to the lattice thermal conductivity, while ZA mode contribution is less because of the quadratic dispersion around the Brillouin zone center, particularly in MoSe 2 due to the phonon anharmonicity, evident from the redshift, especially in optical modes, by increasing temperature. For all the considered 2D crystals, the phonon lifetime values are compelled by transition metal atoms, whereas the group velocity spectrum is dictated by chalcogen atoms. Overall, the lattice thermal conductivity is linearly proportional with inverse temperature.

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Coherent phonon transport in short-period two-dimensional superlattices of graphene and boron nitride

Cited by 35 publications

References 47 publications

Thermal Conductivity of Graphene-hBN Superlattice Ribbons

Thermal Conductivity of Graphene-hBN Superlattice Ribbons

Interplay between total thickness and period thickness in the phonon thermal conductivity of superlattices from the nanoscale to the microscale: Coherent versus incoherent phonon transport

Temperature-dependent phonon spectrum of transition metal dichalcogenides calculated from the spectral energy density: Lattice thermal conductivity as an application

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