Resilience of thermal conductance in defected graphene, silicene, and boron nitride nanoribbons

Wirth, Luke J.; Osborn, Tim H.; Farajian, Amir A.

doi:10.1063/1.4965294

Cited by 9 publications

(6 citation statements)

References 47 publications

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“…Given their buckled atomic structure, [14] silicene nanoribbons (SNRs) have a nonzero energy gap, which can be tuned further by applying external transverse electric fields and doping. [15] A few strategies have also been used to reduce thermal transport in SNRs, including adding substrates, [16,17] surface functionalization, [18] defect, [11,19,20] and strain. [21] These studies provide significant guidance for experimental realization.…”

Section: Introductionmentioning

confidence: 99%

Effect of isotope doping on phonon thermal conductivity of silicene nanoribbons: A molecular dynamics study

Xu¹,

Han²,

Li³

2018

Chinese Phys. B

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Silicene, a silicon analogue of graphene, has attracted increasing research attention in recent years because of its unique electrical and thermal conductivities. In this study, phonon thermal conductivity and its isotopic doping effect in silicene nanoribbons (SNRs) are investigated by using molecular dynamics simulations. The calculated thermal conductivities are approximately 32 W/mK and 35 W/mK for armchair-edged SNRs and zigzag-edged SNRs, respectively, which show anisotropic behaviors. Isotope doping induces mass disorder in the lattice, which results in increased phonon scattering, thus reducing the thermal conductivity. The phonon thermal conductivity of isotopic doped SNR is dependent on the concentration and arrangement pattern of dopants. A maximum reduction of about 15% is obtained at 50% randomly isotopic doping with 30 Si. In addition, ordered doping (i.e., isotope superlattice) leads to a much larger reduction in thermal conductivity than random doping for the same doping concentration. Particularly, the periodicity of the doping superlattice structure has a significant influence on the thermal conductivity of SNR. Phonon spectrum analysis is also used to qualitatively explain the mechanism of thermal conductivity change induced by isotopic doping. This study highlights the importance of isotopic doping in tuning the thermal properties of silicene, thus guiding defect engineering of the thermal properties of two-dimensional silicon materials.

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Section: Introductionmentioning

confidence: 99%

Effect of isotope doping on phonon thermal conductivity of silicene nanoribbons: A molecular dynamics study

Xu¹,

Han²,

Li³

2018

Chinese Phys. B

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“…This shift would also change the chemical potential that maximizes ZT . On the other hand, edge disorder is known to decrease phonon-contributed thermal conductance, so potential trade-offs between this effect and any induced electron–phonon scattering would need to be analyzed.…”

Section: Resultsmentioning

confidence: 99%

“…For each system, we have Gaussian write molecular orbital coefficients and corresponding eigenvalues, which give us the Hamiltonian eigenvalues and eigenvectors. These, along with overlap and force constant matrices, are obtained following optimization and input into our program TARABORD − that calculates electron and phonon transmission coefficients ( T e and T p , respectively) as functions of energy, using the ab initio based nonequilibrium Green’s function (NEGF) method. The method mathematically constructs an infinite open system with a junction consisting of one unit cell and semi-infinite contact nanoribbons consisting of periodically repeated structures to the left and right.…”

Section: Methodsmentioning

confidence: 99%

“…Following geometry optimization, force constant calculations were also performed within Gaussian 09 using the same method and basis set to obtain Hessian matrices containing the second derivative of energy with respect to position for each atom . These matrices were used by our program , to calculate phonon transmission coefficients, T p , as functions of frequency, − based on the NEGF method, using and where ω is phonon frequency, η is a small real number, I is the identity matrix, K C is the junction Hessian, and the rest of the functions are the phonon counterparts of the electron ones used in eqs and .…”

Section: Methodsmentioning

confidence: 99%

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Systematic Enhancement of Thermoelectric Figure of Merit in Edge-Engineered Nanoribbons

Wirth

Farajian

2018

J. Phys. Chem. C

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Nanomaterials provide unique promise to thermoelectric energy conversion owing to their possible phonon confinement and reduced thermal conductivity. These effects can, in particular, occur in nanoribbons upon edge-engineering. Here, we study graphene, boron nitride, and silicene chevron nanoribbons (CNRs) because of their high edge-length to surface area ratio to assess phonon boundary scattering effects on improving the thermoelectric figure of merit (ZT). The ab initio based nonequilibrium Green’s function method is utilized to calculate quantum electronic and phononic thermal conductance, electrical conductance, and Seebeck coefficient. Our results show that, compared to straight nanoribbons, ZT in CNRs is systematically enhanced. Detailed contributions to CNRs’ ZT for different geometries and materials are analyzed, in particular, separation of electrical and electron-contributed thermal conductance versus chemical potential. Taking the corresponding recent fabrications into account, edge-engineering of nanoribbons is shown to provide a possible strategy for achieving competitive thermoelectric energy conversion.

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“…These defects not only significantly affect the electronic properties of the material, but also act as phonon localization/delocalization centers, with the consequent deterioration of the thermal properties. 34,52,53 By using firstprinciples calculation, several authors have studied different configurations of defects in silicene, considering single vacancies, groups of vacancies (clusters), or even extended line of defects. 54,55 In these works, it is shown that due to silicene presents sp 3 hybridization, the formation energy of these defects is reduced, and consequently, the defective silicene becomes a stable structure.…”

Section: A Impact Of Vacancies On the Thermal Conductancementioning

confidence: 99%

Tuning the thermoelectric response of silicene nanoribbons with vacancies

Núñez¹,

Saiz-Bretín²,

Orellana³

et al. 2020

J. Phys.: Condens. Matter

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In this work, we present a thorough study of the thermoelectric properties of silicene nanoribbons in the presence of a random distribution of atomic vacancies. By using a linear approach within the Landauer formalism, we calculate phonon and electron thermal conductances, the electric conductance, the Seebeck coefficient and the figure of merit of the nanoribbons. We found a sizable reduction of the phonon thermal conductance as a function of the vacancy concentration over a wide range of temperature. At the same time, the electric properties are not severely deteriorated, leading to an overall remarkable thermoelectric efficiency. We conclude that the incorporation of vacancies paves the way for designing better and more efficient nanoscale thermoelectric devices.

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Resilience of thermal conductance in defected graphene, silicene, and boron nitride nanoribbons

Cited by 9 publications

References 47 publications

Effect of isotope doping on phonon thermal conductivity of silicene nanoribbons: A molecular dynamics study

Effect of isotope doping on phonon thermal conductivity of silicene nanoribbons: A molecular dynamics study

Systematic Enhancement of Thermoelectric Figure of Merit in Edge-Engineered Nanoribbons

Tuning the thermoelectric response of silicene nanoribbons with vacancies

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