Tuning the Band Structure of Silicene by Surface and Interface Control

该项目由材料研究部（DMR）的电子与光子材料（EPM）和固态与材料化学（SSMC）项目共同资助。非技术描述：在石墨烯中发现的奇异物理现象激发了人们对各种二维（2D）材料的极大科学兴趣。只有一个或几个原子层厚度的二维材料在器件可扩展性和摩尔定律的扩展方面优于块状材料。硅烯是一种单层的硅原子，呈蜂窝状排列，具有适应主流硅基电子学和自旋电子学应用的潜力，该项目侧重于硅烯的探索和能带结构调谐。教育部分包括在跨学科的学术环境中培养研究生，将研究与本科生教育和密歇根州立大学本科生研究经验项目相结合，招募少数民族学生，并通过在大学建立的科学剧院等外展活动将研究传播给更广泛的受众。技术描述：硅烯是一种新兴的二维材料，具有像石墨烯一样的狄拉克物理特性，但具有更大的自旋轨道耦合。迄今为止，大部分硅烯生长都是在Ag（111）衬底上进行的，在二硼化锆和铱上取得了边际成功。然而，与衬底的强相互作用使得分离硅烯和测量其电输运性质变得困难。本项目旨在解决这些关键问题：1)探索硅烯在绝缘衬底（如氮化硼）上的生长，以探究其内在性质；2)通过表面化学功能化调节硅烯的带隙和载流子浓度。宽而连续的能带结构调谐对于探索硅烯的性质及其在开关器件中的潜在应用具有重要意义。采用扫描隧道显微镜/光谱学、非接触式原子力显微镜、紫外光电子能谱和x射线光电子能谱等综合实验方法对硅烯的表面进行了表征，并对其电子结构进行了测量。

The project is jointly funded by the Electronic and Photonic Materials (EPM) and the Solid State and Materials Chemistry (SSMC) Programs, both in the Division of Materials Research (DMR).Non-technical Description: The exotic physical phenomena discovered in graphene have spurred great scientific interest in various two-dimensional (2D) materials. 2D materials with only one or a few atomic layers in thickness are favorable over bulk materials in terms of device scalability and the extension of Moore's law. This project focuses on the exploration and band structure tuning of silicene, a monolayer of Si atoms arranged in a honeycomb pattern, which has the potential to be adapted to the mainstream silicon-based electronics and applications in spintronics. The educational component includes training graduate students in an interdisciplinary academic environment, integrating research with undergraduate education and with the Research Experience for Undergraduates program at Michigan State University, recruiting minority students, and disseminating research to an even broader audience through outreach activities such as Science Theatre that has been established at the University.Technical Description: Silicene is an emerging 2D material with the promise of exhibiting Dirac physics like graphene but of a larger spin-orbit coupling. To date most of the silicene growth has been carried out on Ag(111) substrate, with marginal success on zirconium diboride and iridium. However, the strong interaction with the substrate renders it difficult to isolate silicene and to measure its electrical transport properties. This project aims to address these critical issues by 1) exploring growth of silicene on insulating substrates such as boron nitride in order to probe its intrinsic properties; and 2) tuning the band gap and carrier concentration of silicene via surface chemical functionalization. A wide and continuous tuning of the band structure is important for exploring properties of silicene and its potential applications in switching devices. A comprehensive experimental approach including scanning tunneling microscopy/spectroscopy, non-contact atomic force microscopy, ultraviolet and x-ray photoelectron spectroscopy is taken to characterize the surface and to measure the electronic structures of silicene.