A unified fundamental understanding of interfacial thermal transport is missing due to the complicated nature of interfaces. Because of the difficulty to grow high-quality interfaces and lack of materials characterization, the experimentally measured thermal boundary conductance (TBC) in the literature are usually not the same as the ideally modelled interfaces. This work provides a systematic study of TBC across the highest-quality (atomically sharp, harmonic-matched, and ultraclean) epitaxial (111) Al||(0001) sapphire interfaces to date. The comparison of measured high TBC with theoretical models shows that elastic phonon transport dominates the interfacial thermal transport and other mechanisms play negligible roles. This is confirmed by a nearly constant transmission coefficient by scaling the TBC with the Al heat capacity and sapphire heat capacity with phonon frequency lower than 10 THz. Finally, the findings in this work will impact applications such as electronics thermal management, thermoelectric energy conversion, and battery safety.

由于界面的复杂性，因此缺少对界面热传输的统一基本理解。由于难以生长高质量的界面并且缺乏材料表征，因此文献中实验测量的热边界电导（TBC）通常与理想建模的界面不同。这项工作提供了迄今为止对最高质量（原子尖锐，谐波匹配和超净）外延（111）Al ||（0001）蓝宝石界面的TBC的系统研究。测量的高TBC与理论模型的比较表明，弹性声子输运占界面热输运的主导，而其他机理的作用则微不足道。通过将TBC缩放为Al热容和蓝宝石热容（声子频率低于10 THz），可以通过几乎恒定的传输系数来确认这一点。最后，这项工作的发现将影响电子热管理，热电能量转换和电池安全等应用。