Xiao Peng, Chavez-Angel Emigdio, Chaitoglou Stefanos, Sledzinska Marianna, Dimoulas Athanasios, Sotomayor Torres Clivia M, El Sachat Alexandros
Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain.
Departamento de Física, Universidad Autónoma de Barcelona, Bellaterra, 08193 Barcelona, Spain.
Nano Lett. 2021 Nov 10;21(21):9172-9179. doi: 10.1021/acs.nanolett.1c03018. Epub 2021 Oct 28.
The degree of thermal anisotropy affects critically key device-relevant properties of layered two-dimensional materials. Here, we systematically study the in-plane and cross-plane thermal conductivity of crystalline SnSe films of varying thickness (16-190 nm) and uncover a thickness-independent thermal conductivity anisotropy ratio of about ∼8.4. Experimental data obtained using Raman thermometry and frequency domain thermoreflectance showed that the in-plane and cross-plane thermal conductivities monotonically decrease by a factor of 2.5 with decreasing film thickness compared to the bulk values. Moreover, we find that the temperature-dependence of the in-plane component gradually decreases as the film becomes thinner, and in the range from 300 to 473 K it drops by more than a factor of 2. Using the mean free path reconstruction method, we found that phonons with MFP ranging from ∼1 to 53 and from 1 to 30 nm contribute to 50% of the total in-plane and cross-plane thermal conductivity, respectively.
热各向异性程度对层状二维材料与器件相关的关键特性有着至关重要的影响。在此，我们系统地研究了不同厚度（16 - 190纳米）的晶体SnSe薄膜的面内和面外热导率，并发现其热导率各向异性比率约为8.4，与厚度无关。使用拉曼热测量法和频域热反射法获得的实验数据表明，与块体材料值相比，随着薄膜厚度减小，面内和面外热导率单调下降2.5倍。此外，我们发现随着薄膜变薄，面内热导率分量的温度依赖性逐渐降低，在300至473 K范围内下降超过2倍。使用平均自由程重构方法，我们发现平均自由程范围在约1至53纳米和1至30纳米的声子分别对总面内和面外热导率贡献50%。
