高质量外延硅烯/石墨烯异质结构的构建及输运性质研究

Silicene is the silicon analogue of graphene, which has a buckled honeycomb lattice and Dirac band structure. Silicene has been predicted to have many amazing properties including quantum spin Hall effect, chiral superconductivity and giant magnetoresistance. Its band structure can be tuned by external fields and interfacial interactions. However, silicene is quite active in ambient air, which makes it difficult to fabricate device. In the year 2015, L. Tao et al. proposed a method to transfer silicene by encapsulated delamination with native electrodes. This work solved the problem of dissipation of silicene and is noteworthy in silicene device fabrication. However, when apply to silicene heterostructures, such as silicene/graphene heterostructure, this method must be followed by an addition set of graphene transfer procedure, which makes the whole process low efficient. .In this proposal, we use an in-situ intercalation epitaxial process to make high quality silicene/graphene heterostructure in an ultra-high vacuum (UHV) chamber by means of molecular beam epitaxy and check by scanning tunneling microscopy in the same UHV chamber. The heterostructure made by this recipe can have atomically flat surface and interface. The heterostructure is planned to grow on a single crystal metal thin film on mica, which can be transferred as a whole using L. Tao’s method. A vertical heterosturcture is going to be make to the transport properties of this material. Our proposal is simple and promising, and is ready to fine novel properties in silicene/graphene heterostruture.

硅烯是一种新型二维原子晶体材料，与石墨烯具有类似的晶格结构，即硅原子按六角蜂房结构排布。与石墨烯一样，硅烯有着优异的性质，并且可以直接整合入现有的硅工业。2015年硅烯的第一个场效应晶体管已成功制备出。但因为硅烯在空气中活性较大，转移受诸多限制（如不能在空气中暴露时间过长）因此一直没有实现以硅烯为组成单元的异质结器件。我们参考已有的研究成果、结合自身的研究基础，提出用原位插层外延的方法制备硅烯/石墨烯异质结，并用“胶囊封装”的形式把异质结与原生电极整体转移，有望制备出高质量的硅烯/石墨烯异质结器件，得到器件的输运性质。

硅烯是六角蜂房结构的单原子晶体，有着与石墨烯类似的结构和能带，有直接整合到现有的硅工业产业链中的潜力。硅烯的电子输运性质可以通过外场、界面相互作用等很好地调制，从而得到能够满足微纳电子器件要求的能隙大小和能带结构。硅烯与石墨烯具有类似的能带结构，构筑其垂直方向的异质结有望像双层石墨烯一样打开能隙的同时保持高的载流子迁移率，并会出现双层石墨烯所不具备的性质，如垂直方向的整流性质、手性超导等。另外，目前生长硅烯的基底主要为Ag(111)，在这一基底上生长的硅烯中有较多的畴界，限制了其载流子迁移率，如果能制备出晶畴较少的样品会对硅烯的实际应用有重要意义。.本项目的主要研究内容和重要结果如下：.1. 在Ru(0001)基底上制备了大面积、高质量的硅烯。观察并解释了硅烯在Ru(0001)表面的生长过程，发现了新的硅二维结构。这些发现会对多种硅材料的功能化等方面的研究起到推动作用。.2. 基于外延石墨烯上的原位插层硅插层方法，通过精确控制制备条件，实现了大面积、高质量的石墨烯/硅烯异质结。观察并解释了石墨烯/硅烯异质结的生长过程，结合第一性原理给出了生长机制。对今后生长相似类型的异质结有指导作用。.3. 初步探索了基于硅烯/石墨烯异质结的器件制备与输运性质。.4. 用自下而上的方法制备S掺杂石墨烯纳米带。在不同的退火条件下依次得到硫掺杂的聚合物，硫掺杂的臂章形石墨烯纳米带和本征的边界上掺杂有五元环的臂章形石墨烯纳米带。最终产物具有负的微分电导特性，有助于制备基于臂章形纳米带的整流器和放大器。.通过本项目的实施，证明了原位硅插层方法制备硅烯/石墨烯异质结构的可行性。为使用插层技术得到其它二维材料异质结构提供了参考。