Fig. 2
From: Thermal transport in layer-by-layer assembled polycrystalline graphene films
In-plane thermal properties of layer-by-layer assembled graphene films. a Extracted thermal conductance of graphene and supporting silicon nitride membrane. b Thermal conductance of layer-by-layer assembled graphene films, adjusted to account for variations in sample length. In a, b solid-symbols are data extracted by 3D finite element modeling while open symbols are extracted using a simplified analytical model. c Calculated thermal conductivity from conductance in b compared to data for monocrystalline exfoliated graphene.15 The solid line through the exfoliated data is our calibrated NEGF model16 for monocrystalline graphene.15 d Thermal conductivity of two N = 1 polycrystalline graphene samples with different average grain sizes of 60 ± 30 nm and 140 ± 80 nm by different growths (solid symbols) and data for exfoliated monocrystalline graphene (open squares),15 showing clear grain size dependences at different temperatures. Solid lines are obtained from NEGF calculations and show excellent agreement with the experimental data. e Schematic representation of substrate dampening and grain boundary scattering of graphene phonons. f Comparison of our polycrystalline graphene thermal conductivity to previous reports of suspended graphene,19 substrate-supported exfoliated graphene,15 metal-supported CVD graphene,43 graphene nanoribbons,33 and natural graphite.44 This work adds a “missing piece” to the literature highlighting the role of the substrate and grain boundary scattering in suppressing thermal conductivity in supported polycrystalline graphene over a wide temperature range. Error bars are the estimated experimental uncertainty (Supplementary Information)
