二维金属团簇／硅烯复合结构电子输运性质的研究

Two-dimensional atomic crystals have attracted a lot of attention in the past few years due to their unique physical properties and potential novel applications. Graphene has been most intensively studied and shows promise as a new material with applications in many fields. However, problems arising from its incompatibility with the existing semiconductor industry and zero bandgap may limit its application in the next generation of electronics. Recently, another two-dimensional atomic material, silicene, which is the silicon-based counterpart of graphene, has been theoretically predicted and experimentally achieved on different substrates, such as Ag and Ir, by means of epitaxial growth. Very high electronic mobility and tunable bandgap, as well as the natural compatibility with the existing silicon-based microelectronics industry, make silicene an exciting new candidate for the electronics industry. In this project, we will study the interactions of metal adatoms (and clusters) with high quality silicene and further determine the "two-dimensional metal clusters / silicene" composite structures. Density functional theory calculations had proposed that surface adsorption of metal atoms may change the bandgap and allow for functionalization of silicene opening the possibility for a variety of applications. Furthermore, unlike on graphene, the binding energies of some metal adatoms on silicene are higher than the cohesive energies of the bulk metals, which should lead to the preferential growth of two-dimensional metal clusters rather than three-dimensional ones on the silicene surfaces. The topographic properties, quantum properties and the electronic properties of the silicene before and after the deposition of metal atoms (and clusters) will be investigated by low temperature scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS) and four-probe scanning tunneling potentiometer (STP). The synthesis of the multilayer composite structures will be explored and the electronic transport properties of the structures will be measured. This work will provide a deeper fundamental understanding of silicene functionalization and further its application in the next generation of electronic devices.

硅烯是利用外延生长方法制备出的一种新型二维原子晶体材料。硅烯的电子迁移率高，带隙可调，且和现有的硅基半导体微电子产业兼容，这些其它材料所不具备的优点使得硅烯在电子信息产业中有极大的应用前景。基于密度泛函理论的计算，吸附金属原子可以调控硅烯的带隙；且硅烯表面上一些金属的吸附能大于金属本身内聚能，使得金属在硅烯表面倾向于形成二维层状团簇。本课题将研究不同金属原子和硅烯之间的相互作用，有选择地构建"二维金属团簇／硅烯／基底"复合二维多层结构并研究其基本物性。首先，我们将利用低温扫描隧道显微镜、扫描隧道谱以及四探针扫描隧道电位仪等多种实验手段以及理论分析全面地研究吸附金属原子前后硅烯的形貌、量子态的变化，了解"结构--物性"的关联；然后进一步可控地构建多层复合结构并原位测量其新奇的电学输运性质。通过这一工作，我们将深入理解硅烯材料，为硅烯的功能化并应用于下一代电子器件提供坚实的物理学基础。

充分理解硅烯及其他二维原子晶体材料的本征特性以及这些二维原子晶体材料之间的相互作用，尤其是“结构——物性”的关联，是将硅烯等材料功能化并应用于下一代电子信息器件的基础。该课题进行了相关的研究工作，得到一些结果：1）研究了不同转角、不同滑移量以及不同厚度的氮化硼／硅烯／氮化硼异质结的特性，发现三层或以上的氮化硼可以有效地保护硅烯的本征特性；2）首次构筑了“纳尺度的自然图案”材料：具有周期排列三角形孔洞的单层硒化铜，材料具有选择性功能化以及空气稳定性的特性，预示了潜在的功能化应用前景。3）制备了高质量的双层二硒化钯，不同的衬底上的二硒化钯薄膜的连续性带来了原子尺度锐利的面内异质结，进而原位的实现二维材料面内的功能化。.在项目执行期间，发表SCI论文10篇，包括Nature Materials一篇，Nano Research三篇，ACS Nano一篇，JPCL一篇。申请中国发明专利一项。项目负责人获优秀青年科学基金项目支持开始了另一课题的研究。