Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092 Zürich, Switzerland.
Nanoscale. 2017 Oct 19;9(40):15515-15524. doi: 10.1039/c7nr05346k.
The thermal transport properties of graphene are strongly influenced by its contact environment and the strength of such interactions can be used to tailor these properties. Here we find that annealing suppresses the basal plane thermal conductivity (κ) of graphene supported on silicon dioxide, due to the increased conformity of graphene to the nanoscale asperities of the substrate after annealing. Intriguingly, increasing the polycrystallinity of graphene, grown by chemical vapor deposition on copper, increases the severity of this suppression after annealing, revealing the role of grain boundaries and associated defects in aiding phonon scattering by the substrate. In highly polycrystalline graphene, the value of κ after annealing is comparable to that after significant fluorination of an identical unannealed sample. Our experiments employ the suspended micro-bridge platform for basal plane thermal conductivity measurements. Using xenon difluoride gas for the final release also enables the investigation of thermal transport in graphene in contact with polymers. We find evidence for weaker phonon scattering in graphene, due to a 10 nm thick polymer layer on top compared to the pre-existing silicon dioxide substrate, which is a promising result for flexible electronics applications of graphene.
石墨烯的热传输性质强烈地受到其接触环境的影响，而这种相互作用的强度可以用来调整这些性质。在这里，我们发现退火会抑制氧化硅支撑的石墨烯的基面热导率（κ），这是因为退火后石墨烯更符合基底纳米级的粗糙度。有趣的是，通过化学气相沉积在铜上生长的多晶石墨烯的增加，会增加退火后这种抑制的严重程度，揭示了晶界和相关缺陷在帮助声子与基底散射方面的作用。在高度多晶的石墨烯中，退火后的κ 值与对相同未经退火的样品进行大量氟化后的κ 值相当。我们的实验采用悬浮微桥平台进行基面热导率测量。使用氙二氟化物气体进行最终释放也可以研究与聚合物接触的石墨烯中的热传输。与之前存在的二氧化硅基底相比，我们在顶部发现了一层 10nm 厚的聚合物层，这表明石墨烯的声子散射较弱，这对于石墨烯在柔性电子应用方面是一个有希望的结果。
