Bilateral substrate effect on the thermal conductivity of two-dimensional silicon.
Bilateral substrate effect on the thermal conductivity of two-dimensional silicon.
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DOI：
10.1039/c4nr06523a
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发表时间：
2015-03
期刊：
影响因子：
6.7
通讯作者：
Xiaoliang Zhang;Hua Bao;Ming Hu
中科院分区：
文献类型：
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作者：
Xiaoliang Zhang;Hua Bao;Ming Hu
硅烯是石墨烯的硅基对应物，由于其独特而迷人的物理和化学性质，除了石墨烯之外，还受到了广泛的科学家和工程师的特别关注。最近，原子薄Si层的热输运，在纳米电子学中的各种应用的关键，已被研究;然而，到目前为止，衬底效应还没有被研究。本文采用非平衡分子动力学方法研究了不同衬底上硅烯的声子输运。观察到了一种反直觉的现象，即通过改变衬底的表面晶面可以增强或抑制硅烯的热导率。这种现象与一般理解的支撑型石墨烯（一种代表性的二维材料）有着根本的不同，在支撑型石墨烯中，基底总是对石墨烯的声子输运产生负面影响。通过进行声子极化和光谱能量密度分析，我们解释了新现象的基本物理学，即衬底诱导的硅烯热输运中对主导声子的不同影响：支撑在6 H-SiC衬底上的硅烯的热导率的显著增加是由于大多数声学声子的寿命增加，而载于3C-SiC衬底上的硅烯的热导率的显著降低是由于几乎整个声子谱的寿命的降低。我们的研究结果表明，通过选择不同的基板，硅烯的热导率可以在很大程度上进行调整，这为操纵硅烯的热传输性能为未来新兴的应用铺平了道路。
Silicene, the silicon-based counterpart of graphene, has received exceptional attention from a wide community of scientists and engineers in addition to graphene, due to its unique and fascinating physical and chemical properties. Recently, the thermal transport of the atomic thin Si layer, critical to various applications in nanoelectronics, has been studied; however, to date, the substrate effect has not been investigated. In this paper, we present our nonequilibrium molecular dynamics studies on the phonon transport of silicene supported on different substrates. A counter-intuitive phenomenon, in which the thermal conductivity of silicene can be either enhanced or suppressed by changing the surface crystal plane of the substrate, has been observed. This phenomenon is fundamentally different from the general understanding of supported graphene, a representative two-dimensional material, in which the substrate always has a negative effect on the phonon transport of graphene. By performing phonon polarization and spectral energy density analysis, we explain the underlying physics of the new phenomenon in terms of the different impacts on the dominant phonons in the thermal transport of silicene induced by the substrate: the dramatic increase in the thermal conductivity of silicene supported on the 6H-SiC substrate is due to the augmented lifetime of the majority of the acoustic phonons, while the significant decrease in the thermal conductivity of silicene supported on the 3C-SiC substrate results from the reduction in the lifetime of almost the entire phonon spectrum. Our results suggest that, by choosing different substrates, the thermal conductivity of silicene can be largely tuned, which paves the way for manipulating the thermal transport properties of silicene for future emerging applications.