Yin Yan, Yi Min, Guo Wanlin
State Key Lab of Mechanics and Control of Mechanical Structures & Key Lab for Intelligent Nano Materials and Devices of Ministry of Education & Institute for Frontier Science &Institute of Nanoscience & College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics (NUAA), Nanjing 210016, China.
National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China.
ACS Appl Mater Interfaces. 2021 Sep 29;13(38):45907-45915. doi: 10.1021/acsami.1c14205. Epub 2021 Sep 15.
The lattice thermal conductivity (κ) of a newly synthesized two-dimensional (2D) MoSiN family and its associated abnormality are anatomized by phonon Boltzmann transport calculations. κ of MoSiN and WSiN is found to be over 400 W m K at 300 K. κ of MoSiZ (Z = N, P, As) obeys Slack's rule of thumb, decreasing by 1 order of magnitude from Z = N to Z = As with 46 W m K. However, in MSiN (M = Mo, Cr, W, Ti, Zr, Hf), the variation of κ with respect to M is anomalous, that is, deviating from Slack's classic rule. For M in the same group, κ of MSiN is insensitive to the average atomic mass, Debye temperature, phonon group velocity, and bond strength owing to the similar phonon structure and scattering rates. MSiN with heavy group-VIB M even possesses a 3-4 times higher κ than that with light group-IVB M due to its much stronger M-N and exterior Si-N bonds and thus 1 order of magnitude lower phonon scattering rates. Nevertheless, this abnormality could be traced to an interplay of certain basic vibrational properties including the bunching strength and flatness of acoustic branches and their nearby optical branches, which lie outside of the conventional guidelines by Slack. This work predicts high κ of 2D MSiZ for thermal management and provides microscopic insights into deciphering the anomalous κ of layered 2D structures.
通过声子玻尔兹曼输运计算剖析了新合成的二维（2D）MoSiN族的晶格热导率（κ）及其相关异常情况。发现MoSiN和WSiN在300 K时的κ超过400 W m⁻¹ K⁻¹。MoSiZ（Z = N、P、As）的κ遵循斯莱克经验法则，从Z = N到Z = As，κ以46 W m⁻¹ K⁻¹的幅度下降了1个数量级。然而，在MSiN（M = Mo、Cr、W、Ti、Zr、Hf）中，κ随M的变化是异常的，即偏离了斯莱克的经典规则。对于同一族中的M，由于声子结构和散射率相似，MSiN的κ对平均原子质量、德拜温度、声子群速度和键强不敏感。由于其更强的M-N键和外部Si-N键以及因此低1个数量级的声子散射率，具有重VIB族M的MSiN甚至比具有轻IVB族M的MSiN的κ高3 - 4倍。尽管如此，这种异常情况可追溯到某些基本振动特性的相互作用，包括声学支及其附近光学支的聚集强度和平坦度，这些都超出了斯莱克的传统准则。这项工作预测了二维MSiZ在热管理方面的高κ，并为解读层状二维结构的异常κ提供了微观见解。
