Oommen Shany Mary, Pisana Simone
Department of Physics and Astronomy, York University, Toronto, Canada.
Department of Electrical Engineering and Computer Science, York University, Toronto, Canada.
J Phys Condens Matter. 2021 Feb 24;33(8):085702. doi: 10.1088/1361-648X/abcbd8.
Varying the thermal boundary conductance at metal-dielectric interfaces is of great importance for highly integrated electronic structures such as electronic, thermoelectric and plasmonic devices where heat dissipation is dominated by interfacial effects. In this paper we study the modification of the thermal boundary conductance at metal-dielectric interfaces by inserting metal interlayers of varying thickness below 10 nm. We show that the insertion of a tantalum interlayer at the Al/Si and Al/sapphire interfaces strongly hinders the phonon transmission across these boundaries, with a sharp transition and plateau within ∼1 nm. We show that the electron-phonon coupling has a major influence on the sharpness of the transition as the interlayer thickness is varied, and if the coupling is strong, the variation in thermal boundary conductance typically saturates within 2 nm. In contrast, the addition of a nickel interlayer at the Al/Si and the Al/sapphire interfaces produces a local minimum as the interlayer thickness increases, due to the similar phonon dispersion in Ni and Al. The weaker electron-phonon coupling in Ni causes the boundary conductance to saturate more slowly. Thermal property measurements were performed using time domain thermo-reflectance and are in good agreement with a formulation of the diffuse mismatch model based on real phonon dispersions that accounts for inelastic phonon scattering and phonon confinement within the interlayer. The analysis of the different assumptions included in the model reveals when inelastic processes should be considered. A hybrid model that introduces inelastic scattering only when the materials are more acoustically matched is found to better predict the thickness dependence of the thermal boundary conductance without any fitting parameters.
对于诸如电子、热电和等离子体设备等高度集成的电子结构而言，改变金属 - 电介质界面处的热边界电导至关重要，在这些结构中，热耗散主要由界面效应主导。在本文中，我们研究了通过插入厚度小于10 nm的不同金属中间层来改变金属 - 电介质界面处的热边界电导。我们表明，在Al/Si和Al/蓝宝石界面处插入钽中间层会强烈阻碍声子穿过这些边界的传输，在约1 nm范围内有一个急剧的转变和平台期。我们表明，随着中间层厚度的变化，电子 - 声子耦合对转变的锐度有重大影响，并且如果耦合很强，热边界电导的变化通常在2 nm内达到饱和。相比之下，在Al/Si和Al/蓝宝石界面处添加镍中间层会随着中间层厚度的增加产生一个局部最小值，这是由于Ni和Al中声子色散相似。Ni中较弱的电子 - 声子耦合导致边界电导饱和得更慢。使用时域热反射法进行了热性能测量，结果与基于真实声子色散的漫反射失配模型的公式很好地吻合，该模型考虑了非弹性声子散射和中间层内的声子限制。对模型中包含的不同假设的分析揭示了何时应考虑非弹性过程。发现一种仅在材料声学匹配性更好时引入非弹性散射的混合模型能够在没有任何拟合参数的情况下更好地预测热边界电导的厚度依赖性。
