Isotope effect on the thermal expansion coefficient of atomically thin boron nitride
Isotope effect on the thermal expansion coefficient of atomically thin boron nitride
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DOI：
10.1088/2053-1583/ac0730
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发表时间：
2021
期刊：
影响因子：
5.5
通讯作者：
Qiran Cai;E. Janzen;J. Edgar;Weiliang Gan;Shunyi Zhang;E. Santos;Luhua Li
中科院分区：
文献类型：
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作者：
Qiran Cai;E. Janzen;J. Edgar;Weiliang Gan;Shunyi Zhang;E. Santos;Luhua Li
原子薄的单同位素六方氮化硼（BN）具有电绝缘性和高导热性，可用作电子封装材料中的填料，用于集成和小型化现代设备中的散热。电子封装中的热膨胀失配可能会导致应变并最终导致设备故障，因此测量和了解原子薄同位素纯 BN 的热膨胀系数 (TEC) 非常有价值。在这项工作中，我们使用拉曼光谱和包括范德华色散力的密度泛函理论计算研究了单层、双层和三层同位素纯化的 BN 的 TEC。在接近室温时，单层 (1L) 10BN 的实验 TEC 比 1L 11BN 稍大：分别为 (−5.1 ± 0.8) × 10−6 K−1 和 (−4.6 ± 0.8) × 10−6 K−1。高达 700 K 的负 TEC 归因于 BN 面内伸缩振动模式和面外弯曲模式之间的竞争；较轻的同位素由于其面外弯曲模式的振幅较高，导致绝对 TEC 较大。同位素BN的绝对TEC随着原子厚度的增加而降低，这表明面外弯曲刚度的增强。对同位素对二维 (2D) 材料 TEC 效应的深入了解也为最大限度地减少 2D 范德华异质结构中 TEC 失配开辟了一条有希望的途径。
Atomically thin monoisotopic hexagonal boron nitride (BN) which is electrically insulating and has a high thermal conductivity could be utilized as fillers in electronic packaging materials for thermal dissipation in integrated and miniaturized modern devices. Thermal expansion mismatch in electronic packaging could cause strain and ultimately device failure, so it is valuable to measure and understand the thermal expansion coefficient (TEC) of atomically thin isotopically pure BN. In this work, we studied the TECs of mono-, bi-, and tri-layer isotope-purified BN using Raman spectroscopy and density functional theory calculations including van der Waals dispersion forces. Monolayer (1L) 10BN had a slightly larger experimental TEC than 1L 11BN at close to room temperature: (−5.1 ± 0.8) × 10−6 K−1 and (−4.6 ± 0.8) × 10−6 K−1, respectively. The negative TECs up to 700 K were attributed to the competition between the in-plane stretching vibration modes and out-of-plane bending modes in BN; the lighter isotope leads to a larger absolute TEC due to higher amplitude of its out-of-plane bending modes. The absolute TECs of isotopic BN decreased with increased atomic thickness, which indicates strengthening of the out-of-plane bending rigidity. The deep understanding of the isotope effect on the TEC of two-dimensional (2D) materials also opens a promising pathway to minimize TEC mismatch in 2D van der Waals heterostructures.