title: Bimodal Phonon Scattering in Graphene Grain Boundaries.
abstract: Graphene has served as the model 2D system for over a decade, and the effects of grain boundaries (GBs) on its electrical and mechanical properties are very well investigated. However, no direct measurement of the correlation between thermal transport and graphene GBs has been reported. Here, we report a simultaneous comparison of thermal transport in supported single crystalline graphene to thermal transport across an individual graphene GB. Our experiments show that thermal conductance (per unit area) through an isolated GB can be up to an order of magnitude lower than the theoretically anticipated values. Our measurements are supported by Boltzmann transport modeling which uncovers a new bimodal phonon scattering phenomenon initiated by the GB structure. In this novel scattering mechanism, boundary roughness scattering dominates the phonon transport in low-mismatch GBs, while for higher mismatch angles there is an additional resistance caused by the formation of a disordered region at the GB. Nonequilibrium molecular dynamics simulations verify that the amount of disorder in the GB region is the determining factor in impeding thermal transport across GBs.
authors.forename: Poya
authors.initials: P
authors.lastname: Yasaei
authors.forename: Arman
authors.initials: A
authors.lastname: Fathizadeh
authors.forename: Reza
authors.initials: R
authors.lastname: Hantehzadeh
authors.affiliation: §Electrical and Computer Engineering Department, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States.
authors.forename: Arnab K
authors.initials: AK
authors.lastname: Majee
authors.affiliation: ∥Department of Civil and Material Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, United States.
authors.forename: Ahmed
authors.initials: A
authors.lastname: El-Ghandour
authors.affiliation: ⊥Department of Materials Science and Engineering, Boise State University, Boise, Idaho 83725, United States.
authors.forename: David
authors.initials: D
authors.lastname: Estrada
authors.affiliation: ∥Department of Civil and Material Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, United States.
authors.forename: Craig
authors.initials: C
authors.lastname: Foster
authors.affiliation: §Electrical and Computer Engineering Department, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States.
authors.forename: Zlatan
authors.initials: Z
authors.lastname: Aksamija
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Khalili-Araghi
authors.forename: Amin
authors.initials: A
authors.lastname: Salehi-Khojin
keywords: Boltzmann transport modeling; Graphene; electrical thermometry; grain boundaries; molecular dynamics; thermal transport