北京大学高鹏团队近日实现了用电子显微镜探测声子在界面上的输运动力学。2025年6月11日，《自然》杂志发表了这一成果。

了解材料界面上的热传输机制对于推进半导体技术至关重要，特别是在极端功率密度下运行的小型化器件中。尽管界面声子介导过程在理论上被确立为半导体界面热输运的主要机制，但由于测量埋入界面上的温度和非平衡声子分布的挑战，它们的纳米级动力学在实验上仍然难以捉摸。 

研究组通过在电子显微镜中使用原位振动电子能量损失光谱（EELS）来克服这些局限性，以在热输运过程中描绘AlN-SiC界面上的纳米级温度梯度，并以亚纳米分辨率绘制其非平衡声子占位图。他们观察到温度在2 nm左右急剧下降，能够直接提取相对界面热阻（ITR）。在热输运过程中，界面处声子模热导率的失配会导致附近出现大量非平衡声子，使界面模数量在正向和反向热流下不同，并导致界面约3nm内AlN光学声子的模态温度发生显著变化。这些结果揭示了（亚）纳米尺度的声子输运动力学，并建立了界面模式涉及的非弹性声子散射机制，为热界面工程提供了有价值的见解。

附：英文原文

Title: Probing phonon transport dynamics across an interface by electron microscopy

Author: Liu, Fachen, Mao, Ruilin, Liu, Zhiqiang, Du, Jinlong, Gao, Peng

Issue&Volume: 2025-06-11

Abstract: Understanding thermal transport mechanisms across material interfaces is crucial for advancing semiconductor technologies, particularly in miniaturized devices operating under extreme power densities1,2. Although the interface phonon-mediated processes are theoretically established3,4,5,6 as the dominant mechanism for interfacial thermal transport in semiconductors7, their nanoscale dynamics remain experimentally elusive owing to challenges in measuring the temperature and non-equilibrium phonon distributions across the buried interface8,9,10,11. Here we overcome these limitations by using in situ vibrational electron energy-loss spectroscopy (EELS) in an electron microscope to nanoscale profile temperature gradients across the AlN–SiC interface during thermal transport and map its non-equilibrium phonon occupations at sub-nanometre resolution. We observe a sharp temperature drop within about 2nm across the interface, enabling direct extraction of relative interfacial thermal resistance (ITR). During thermal transport, the mismatch of phonon modes’ thermal conductivity at the interface causes substantial non-equilibrium phonons nearby, making the populations of interface modes different under forward and reverse heat flow and also leading to marked changes in the modal temperature of AlN optical phonons within about 3nm of the interface. These results reveal the phonon transport dynamics at the (sub-)nanoscale and establish the inelastic phonon scattering mechanism involved by interface modes, offering valuable insights into the engineering of thermal interfaces.

DOI: 10.1038/s41586-025-09108-6

Source: https://www.nature.com/articles/s41586-025-09108-6