锯齿型石墨烯纳米带电子和自旋性质的实验研究

Zigzag graphene nanoribbions are predicted to have spin-spin interaction induced band gaps and spin polarized edge states, which possibly makes them as core elements for graphene-based spintronic devices. However, it’s so difficult to prepare graphene nanoribbons that only a few experimental papers on electronic properties of graphene nanoribbons have been reported so far. Moreover, graphene nanoribbons are usually grown on metal substrates, as a result, the intrinsic electronic structures can be hardly observed. In our earlier experiments, using in-situ metal nanoparticle-assisted cutting of multilayer graphene films, we prepared zigzag graphene nanoribbons on graphene substrate instead, and observed very robust edge states and significant increase in band gap caused by many-body effect. In this project, we will use low temperature spin polarized scanning tunneling microscope to study the spin density distribution in zigzag graphene nanoribbons and explore how to tune their electronic and spin properties. We hope the project will promote the fundamental researches and potential applications in graphene-based electronic and spintronic devices.

早期的理论研究表明锯齿型石墨烯纳米带不仅有自旋作用诱导的能隙，而且还有自旋极化的边缘态，这使得其可能成为基于石墨烯的自旋电子器件的核心元件。实验制备石墨烯纳米带非常困难，也就是最近几年才有报道。而且石墨烯纳米带大多都是在金属衬底上生长的，所以很难观测到纳米带本征的电子结构。利用金属纳米颗粒原位切割多层石墨烯薄膜的方法，我们在石墨烯衬底上不仅成功制备出锯齿型石墨烯纳米带，而且观测到信号非常强的边缘态以及多体效应诱导增大的能隙。本项目将在此基础上利用低温自旋极化扫描隧道显微镜研究石墨烯纳米带中自旋的分布以及如何对纳米带电子和自旋性质进行调控，希望能够促进石墨烯电子和自旋器件的基础研究和应用方面的发展。

石墨烯纳米结构有望在未来碳基器件中成为核心部件，所以制备石墨烯纳米结构以及探测其电子和自旋性质具有重要的研究意义。在该项目中，我们利用金属颗粒在气体氛围内切割热解碳化硅得到的石墨烯薄膜，制备出各种石墨烯纳米结构，并用低温扫描隧道显微镜成功探测到石墨烯纳米结构边缘的电子态。不仅制备出了氢终止的石墨烯纳米结构，而且制备出了氧终止的石墨烯纳米结构。虽然金属纳米颗粒的直径远大于碳化硅表面的石墨烯薄膜厚度，但是通过控制气体压强，可以使金属颗粒只切割最上层的石墨烯。利用金属颗粒刻蚀石墨烯纳米带的方法有望制备出OH、NH、NO等多种终止的石墨烯纳米带及其他形状的石墨烯纳米结构。在项目执行期间还在其它相关体系中探测到一系列新奇的物理现象，共发表SCI论文22篇。这些成果对研究磁耦合机制，边缘态与超导态的相互作用等具有重要的价值。