Structure-specific, mode-resolved phonon coherence and specularity at graphene grain boundaries

Abstract

In spite of their importance for understanding phonon transport phenomena in thin films and polycrystalline solids, the effects of boundary roughness scattering on phonon specularity and coherence are poorly understood because there is no general method for predicting their dependence on phonon momentum, frequency, branch and boundary morphology. Using the recently formulated atomistic S-matrix method, we develop a theory of boundary roughness scattering to determine the mode-resolved phonon coherence and specularity parameters from the scattering amplitudes. To illustrate the theory, we apply it to phonon scattering in realistic nonsymmetric graphene grain boundary (GB) models derived from atomic structure predictions. The method is validated by comparing its predictions with frequency-resolved results from lattice dynamics-based calculations. We prove that incoherent scattering is almost perfectly diffusive. We show that phonon scattering at the graphene GB is not diffuse although coherence and specularity are significantly reduced for long-wavelength flexural acoustic phonons. Our approach can be generalized to other atomistic boundary models.

7 pages, 5 figures

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Cited by in corpus (5)

• Evaluation of diffuse mismatch model for phonon scattering at disordered interfaces
• Specular transmission and diffuse reflection in phonon scattering at grain boundary
• The Atomistic Green's Function method for acoustic and elastic wave-scattering problems
• Effect of boundary roughness on the attenuation of specular phonon reflection in graphene
• Control of wave scattering for robust coherent transmission in a disordered medium