Trabelsi A Ben Gouider, Kusmartsev F V, Robinson B J, Ouerghi A, Kusmartseva O E, Kolosov O V, Mazzocco R, Gaifullin Marat B, Oueslati M
Nanotechnology. 2014 Apr 25;25(16):165704. doi: 10.1088/0957-4484/25/16/165704.
For the first time, new epitaxial graphene nano-structures resembling charged 'bubbles' and 'domes' are reported. A strong influence, arising from the change in morphology, on the graphene layer's electronic, mechanical and optical properties has been shown. The morphological properties of these structures have been studied with atomic force microscopy (AFM), ultrasonic force microscopy (UFM) and Raman spectroscopy. After initial optical microscopy observation of the graphene, a detailed description of the surface morphology, via AFM and nanomechanical UFM measurements, was obtained. Here, graphene nano-structures, domes and bubbles, ranging from a few tens of nanometres (150–200 nm) to a few μm in size have been identified. The AFM topographical and UFM stiffness data implied the freestanding nature of the graphene layer within the domes and bubbles, with heights on the order of 5–12 nm. Raman spectroscopy mappings of G and 2D bands and their ratio confirm not only the graphene composition of these structures but also the existence of step bunching, defect variations and the carrier density distribution. In particular, inside the bubbles and substrate there arises complex charge redistribution; in fact, the graphene bubble–substrate interface forms a charged capacitance. We have determined the strength of the electric field inside the bubble–substrate interface, which may lead to a minigap of the order of 5 meV opening for epitaxial graphene grown on 4H-SiC face-terminated carbon.
首次报道了类似带电“气泡”和“穹顶”的新型外延石墨烯纳米结构。研究表明，形态变化对石墨烯层的电学、力学和光学性质产生了强烈影响。利用原子力显微镜（AFM）、超声力显微镜（UFM）和拉曼光谱对这些结构的形态特性进行了研究。在对石墨烯进行初步光学显微镜观察后，通过AFM和纳米力学UFM测量获得了表面形态的详细描述。在此，已识别出尺寸从几十纳米（150 - 200 nm）到几微米不等的石墨烯纳米结构、穹顶和气泡。AFM形貌和UFM刚度数据表明，穹顶和气泡内的石墨烯层具有独立性质，高度约为5 - 12 nm。G带和2D带的拉曼光谱映射及其比值不仅证实了这些结构的石墨烯组成，还证实了台阶聚集、缺陷变化和载流子密度分布的存在。特别是，在气泡和衬底内部会出现复杂的电荷重新分布；实际上，石墨烯气泡 - 衬底界面形成了一个带电电容。我们已经确定了气泡 - 衬底界面内电场的强度，这可能导致在4H - SiC面端接碳上生长的外延石墨烯出现约5 meV量级的能隙开口。
