功能化介导石墨烯纳米片中的热传输
Functionalization mediates heat transport in graphene nanoflakes
摘要：
自发热是大功率微电子器件面临的一个严重问题。石墨烯和少层石墨烯由于其非常高的面内热导率而引起了人们对散热的极大关注。然而，这种高热导率经历了与衬底的接触和官能化诱导的点缺陷引起的严重退化。在这里，我们表明，微加热器的热管理可以通过引入替代的热逃逸通道来显著改善，该热逃逸通道由通过硅烷分子共价键合到官能化氧化石墨烯的石墨烯基膜实现。理论和实验结果表明，这种石墨烯基膜的热导率的反直觉增强。这种负载型石墨烯的面内热导率的增加伴随着石墨烯-基底热接触的改善。使用红外热成像，我们表明，热点的温度可以降低12 $^o$ C在晶体管中工作在130 W mm $^{-2}$，这对应于一半的数量级增加的设备寿命。从头算和分子动力学模拟表明，功能化抑制了低频声子的跨平面散射，从而通过恢复较长的弯曲声子寿命来增强键合石墨烯膜的面内热传导。
英文摘要：
Self-heating is a severe problem for high-power microelectronic devices. Graphene and few-layer graphene have attracted tremendous attention for heat removal thanks to their extraordinarily high in-plane thermal conductivity. However, this high thermal conductivity undergoes severe degradations caused by the contact with the substrate and the functionalization-induced point defects. Here we show that thermal management of a micro heater can be substantially improved via introduction of alternative heat-escaping channels implemented with graphene-based film covalently bonded to functionalized graphene oxide through silane molecules. Theoretical and experimental results demonstrate a counter-intuitive enhancement of the thermal conductivity of such a graphene-based film. This increase in the in-plane thermal conductivity of supported graphene is accompanied by an improvement on the graphene-substrates thermal contact. Using infrared thermal imaging, we demonstrate that the temperature of the hotspots can be lowered by 12 $^o$C in transistors operating at 130 W mm$^{-2}$ , which corresponds to half of an order-of-magnitude increase in the device lifetime. Ab initio and molecular dynamics simulations reveal that the functionalization constrains the cross-plane scattering of low frequency phonons, which in turn enhances in-plane heat conduction of the bonded graphene film by recovering the long flexural phonon lifetime.
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