Thermal Transport of Novel Two-dimensional Silicon

石墨烯是一种二维原子薄蜂窝晶格，具有许多惊人的物理性质，原则上可以被认为是所有碳同素异形体的基本构件。自从2004年的最新进展以来，石墨烯的研究领域迅速发展起来。石墨烯科学的这些发展促进了前所未有的活动和新物理现象的展示。尽管石墨烯取得了成功，但由于其半金属或零禁带半导体的性质以及与当前硅基技术的不兼容，石墨烯仍然面临着一些严重的问题。鉴于蜂窝几何结构与石墨烯的一些特殊性质有关，人们有强烈的动机研究将碳改变为其他原子类型是否也会产生新的物理现象。一个直观的想法是研究它的类似物--硅烯。实际上，硅烯作为石墨烯的硅对应物，可以很好地解决上述问题，因此最近受到了人们的强烈关注。由于热输运在纳米电子学中的热分散和热电能量转换等许多应用中起着至关重要的作用，因此对硅烯结构的热(主要是声子)输运性质的表征已经成为一个新的需求。此外，我们的初步结果表明，尽管硅烯和石墨烯的蜂窝状晶格结构相似，但它们表现出了一些新的热输运性质，这些性质与石墨烯完全不同。因此，这种反常的物理性质，主要源于其独特的低屈曲结构，可能使硅烯为革命性的电子器件和能量转换材料开辟全新的可能性。在这种最先进的状态下，当前的提议旨在进行各种形式的硅烯纳米结构热传输的理论研究。这种结构中的热传递不仅直接关系到优化相关器件的性能，如改善纳米电子设备的热管理和热电能量转换效率，而且对于许多其他类似的二维系统来说，也是一个科学基础问题。这项提议的总体目标是推进硅烯结构作为新兴技术的新型二维材料的热传输的基本原理。为此，提出了紧密联系和相互依赖的经典分子动力学模拟、基于从头算的非平衡格林函数、非简谐晶格动力学和玻尔兹曼输运方程相结合的方法。这项研究可能会对硅烯和更广泛的二维材料的热传输机理的基本理解提供重大进展，并有可能对高性能纳米电子学的发展和未来的能源需求做出明确的贡献。

Graphene, a two-dimensional atomic thin honeycomb lattice, exhibits numerous striking physical properties, and can, in principle, be considered as an elementary building block for all carbon allotropes. Ever since the recent developments in 2004, the field of graphene research took off rapidly. These developments in the science of graphene prompted an unprecedented surge of activity and demonstration of new physical phenomena. Despite its success, graphene still faces some severe problems in its nature of semi-metal or zero band-gap semiconductor and its incompatibility with the current Si-based technology. Given that the honeycomb geometry is related to some of the exceptional properties of graphene, there is strong motivation to investigate whether changing carbon to other atom type might give rise to novel physical phenomena as well. An intuitive idea is to study its analog - silicene. Acutally, silicene, the Si counterpart of graphene, can solve the above problems smoothly and thus has received intense interest lately. Given the fact that thermal transport plays a critical role in many applications such as heat dissipartion in nanoelectronics and thermoelectric energy conversion, there has been an emerging demand in characterizing thermal (mainly phonons) transport property of silicene structures. Moreover, our preliminary results have shown that silicene exhibits a few novel thermal transport properties, which are fundamentally different from that of graphene, despite the similarity of their honeycomb lattice structure. Therefore, the abnormal physical property, primarily stemming from its unique low buckling structure, may enable silicene to open up entirely new possibilities for revolutionary electronic devices and energy conversion materials. With this state of the art, the current proposal aims to perform theoretical investigations of thermal transport of silicene nanostructures in various forms. Heat transfer in such structures is not only directly relevant to optimizing the relevant device performance such as improved thermal management for nanoelectronics and thermoelectric energy conversion efficiency, but also is a scientifically fundamental problem for many other similar two-dimensional systems. The overall objective of this proposal is to advance the fundamentals underlying the thermal transport of silicene structures as novel two-dimensional material for emerging technologies. Closely linked and interdependent classical molecular dynamics simulations and ab initio based nonequilibrium Greens function and combined anharmonic lattice dynamics and Boltzmann transport equation are proposed as approaches to this end. The investigation is likely to provide a major advancement to the fundamental understanding of thermal transport mechanism of silicene and more broadly two-dimensional materials, with the potential to make a clear contribution to development of high performance nanoelectronics and the energy needs of the future.