Abstract
Understanding the influence of grain boundaries (GBs) on the electrical and thermal transport properties of graphene films is essentially important for electronic, optoelectronic and thermoelectric applications. Here we report a segregation–adsorption chemical vapour deposition method to grow well-stitched high-quality monolayer graphene films with a tunable uniform grain size from ∼200 nm to ∼1 μm, by using a Pt substrate with medium carbon solubility, which enables the determination of the scaling laws of thermal and electrical conductivities as a function of grain size. We found that the thermal conductivity of graphene films dramatically decreases with decreasing grain size by a small thermal boundary conductance of ∼3.8 × 109 W m−2 K−1, while the electrical conductivity slowly decreases with an extraordinarily small GB transport gap of ∼0.01 eV and resistivity of ∼0.3 kΩ μm. Moreover, the changes in both the thermal and electrical conductivities with grain size change are greater than those of typical semiconducting thermoelectric materials.
Highlights
Understanding the influence of grain boundaries (GBs) on the electrical and thermal transport properties of graphene films is essentially important for electronic, optoelectronic and thermoelectric applications
In addition to studies of individual GBs, understanding the influence of grain size on the overall electrical and thermal transport properties of graphene films on a large scale is fundamental and technologically important in order to tune their properties for electronic, optoelectronic and thermoelectric applications[12,13,14,15,16,17,18,19,20,21,22,23,24]. These studies strongly depend on the controlled synthesis of graphene films with tunable and uniform grain size that is smaller than the phonon and electron mean free paths (B a few hundreds of nanometres) because the contributions to electrical and thermal transports due to scattering from GBs are more significant in this range
We found that the GBs begin to dominant the electrical conductivity of the polycrystalline graphene films only when the grain size is smaller than lgE0.8 mm
Summary
Understanding the influence of grain boundaries (GBs) on the electrical and thermal transport properties of graphene films is essentially important for electronic, optoelectronic and thermoelectric applications. In addition to studies of individual GBs, understanding the influence of grain size on the overall electrical and thermal transport properties of graphene films on a large scale is fundamental and technologically important in order to tune their properties for electronic, optoelectronic and thermoelectric applications[12,13,14,15,16,17,18,19,20,21,22,23,24]. The influence of grain size on the overall thermal conductivity of graphene films remains unknown
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