近常压表征技术在少层石墨烯可控堆垛中的应用

In the process of graphene transition to graphite, the unique photoelectric properties of graphene will undergo dramatic changes as the layer number increases and finally approach to graphite’s properties. The achievement of well-controlled growth of few-layer graphene (monolayer to trilayer graphene) is critical to opening graphene band gap, which has attracted extensive attention. Electron transfer behavior inner/inter graphene layers can be affected by the stacking sequences and rotation angles, recent study even shows that the bilayer graphene can be converted from insulator to superconductor by twisting the angles between the two layers. In this project, graphene nucleation and coalescence will be studied by near ambient pressure characterization techniques. In detail, the graphene stacking growth and etching dynamic process in the controlled atmosphere will be investigated by mainly using near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and near ambient pressure scanning tunneling microscopy (NAP-STM) combined system. The controllable stacking of few-layer graphene is expected to be obtained by operando study of the bottom-up preparation method of graphene growth.

由少层石墨烯转变为体相石墨的过程中，石墨烯独特的光电性能会随着层数的增加而发生变化，逐步接近体相石墨的性质。实现少层（1-3层）单晶质量的石墨烯可控堆垛对打开石墨烯的带隙至关重要，因而引起了广泛的关注。不仅如此，少层石墨烯的堆垛次序以及相对旋转角度能够影响电子在石墨烯层内以及层间中的传输，不同角度堆叠的双层石墨烯甚至可以实现从绝缘体到超导体的转变。本项目将利用近常压表征技术，主要包括近常压X射线光电子能谱与近常压扫描隧道显微镜联用系统，原位研究石墨烯在不同金属表面上的成核与畴区拼合过程，探究近常压可控气氛下少层石墨烯的可控堆垛生长与刻蚀。通过原位研究自下而上的石墨烯制备方法，期望得到可控堆垛的少层石墨烯。

本项目针对少层石墨烯的可控生长及其表界面结构调控两个关键科学问题，借助超真空互联表面成像和谱线技术原位研究手段，揭示了生长过程中的难以捕捉的核心基元步骤和微观机制。取得了以下成果：（1）探明气氛条件、表界面相互作用对单层石墨烯生长、拼接和刻蚀等关键中间过程的影响；（2）实现了均匀双层石墨烯的“层—层”生长及堆垛结构的调控；（3）将少层石墨烯研究中的构建方法和生长机制拓展至其他类似材料，实现了h-BN和石墨烯/h-BN异质结的可控制备，阐明了其外延拼接和堆垛机理。以通讯作者在Advanced Functional Materials, Journal of Physical Chemistry Letters, Nano Research, Carbon等高水平期刊发表论文8篇，申请发明专利3项（其中授权1项），培养博士生1名，硕士生3名。本项目旨在进一步理解少层石墨烯的成核、生长、拼接和堆垛机制，并由此获得的科学规律和实验基础拓展至其他二维材料可控制备。