Anufriev Roman, Gluchko Sergei, Volz Sebastian, Nomura Masahiro
Institute of Industrial Science , The University of Tokyo , Tokyo 153-8505 , Japan.
Laboratory for Integrated Micro Mechatronic Systems/National Center for Scientific Research-Institute of Industrial Science (LIMMS/CNRS-IIS) , The University of Tokyo , Tokyo 153-8505 , Japan.
ACS Nano. 2018 Dec 26;12(12):11928-11935. doi: 10.1021/acsnano.8b07597. Epub 2018 Nov 12.
Future of silicon-based microelectronics depends on solving the heat dissipation problem. A solution may lie in a nanoscale phenomenon known as ballistic heat conduction, which implies conduction of heat without heating the conductor. However, attempts to demonstrate this phenomenon experimentally are controversial and scarce, whereas its mechanism in confined nanostructures is yet to be fully understood. Here, we experimentally demonstrate quasi-ballistic heat conduction in silicon nanowires (NWs). We show that the ballisticity is the strongest in short NWs at low temperatures but weakens as the NW length or temperature is increased. Yet, even at room temperature, quasi-ballistic heat conduction remains visible in short NWs. To better understand this phenomenon, we probe directions and lengths of phonon flights. Our experiments and simulations show that the quasi-ballistic phonon transport in NWs is essentially the Lévy walk with short flights between the NW boundaries and long ballistic leaps along the NW. Thus, we conclude that ballistic heat conduction is present in silicon even at room temperature in sufficiently small nanostructures and may yet improve thermal management in silicon-based microelectronics.
硅基微电子学的未来取决于解决散热问题。一种解决方案可能在于一种被称为弹道热传导的纳米级现象，这意味着热量在不加热导体的情况下传导。然而，通过实验证明这一现象的尝试存在争议且数量稀少，而其在受限纳米结构中的机制尚未完全被理解。在此，我们通过实验证明了硅纳米线（NWs）中的准弹道热传导。我们表明，弹道性在低温下的短纳米线中最强，但随着纳米线长度或温度的增加而减弱。然而，即使在室温下，准弹道热传导在短纳米线中仍然可见。为了更好地理解这一现象，我们探测了声子飞行的方向和长度。我们的实验和模拟表明，纳米线中的准弹道声子输运本质上是一种列维行走，在纳米线边界之间有短程飞行，沿着纳米线有长程弹道跳跃。因此，我们得出结论，即使在室温下，在足够小的纳米结构中硅中也存在弹道热传导，并且这可能会改善硅基微电子学中的热管理。
