Aryana Kiumars, Stewart Derek A, Gaskins John T, Nag Joyeeta, Read John C, Olson David H, Grobis Michael K, Hopkins Patrick E
Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, USA.
Western Digital Corporation, San Jose, CA, USA.
Nat Commun. 2021 May 14;12(1):2817. doi: 10.1038/s41467-021-22999-z.
Amorphous chalcogenide alloys are key materials for data storage and energy scavenging applications due to their large non-linearities in optical and electrical properties as well as low vibrational thermal conductivities. Here, we report on a mechanism to suppress the thermal transport in a representative amorphous chalcogenide system, silicon telluride (SiTe), by nearly an order of magnitude via systematically tailoring the cross-linking network among the atoms. As such, we experimentally demonstrate that in fully dense amorphous SiTe the thermal conductivity can be reduced to as low as 0.10 ± 0.01 W m K for high tellurium content with a density nearly twice that of amorphous silicon. Using ab-initio simulations integrated with lattice dynamics, we attribute the ultralow thermal conductivity of SiTe to the suppressed contribution of extended modes of vibration, namely propagons and diffusons. This leads to a large shift in the mobility edge - a factor of five - towards lower frequency and localization of nearly 42% of the modes. This localization is the result of reductions in coordination number and a transition from over-constrained to under-constrained atomic network.
非晶硫属化物合金因其在光学和电学性质方面的大非线性以及低振动热导率，成为数据存储和能量收集应用的关键材料。在此，我们报告一种机制，通过系统地调整原子间的交联网络，将代表性非晶硫属化物体系碲化硅（SiTe）中的热输运抑制近一个数量级。据此，我们通过实验证明，在完全致密的非晶SiTe中，对于高碲含量，热导率可降低至低至0.10±0.01W m⁻¹ K⁻¹，其密度几乎是非晶硅的两倍。通过结合晶格动力学的第一性原理模拟，我们将SiTe的超低热导率归因于振动扩展模式（即传播子和扩散子）贡献的抑制。这导致迁移率边向低频大幅移动——移动了五倍——并且近42%的模式发生局域化。这种局域化是配位数减少以及原子网络从过度约束向欠约束转变的结果。
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