Strain relaxation in different shapes of single crystal graphene grown by chemical vapor deposition on copper
Strain relaxation in different shapes of single crystal graphene grown by chemical vapor deposition on copper
复制标题
DOI：
10.1016/j.carbon.2020.07.025
复制
发表时间：
2020-07
期刊：
影响因子：
10.9
通讯作者：
T. Nanayakkara;U. Wijewardena;S. Withanage;A. Kriisa;Rasanga L. Samaraweera;R. Mani
中科院分区：
文献类型：
--
作者：
T. Nanayakkara;U. Wijewardena;S. Withanage;A. Kriisa;Rasanga L. Samaraweera;R. Mani
单晶石墨烯在多晶铜箔上的化学气相沉积（CVD）生长是一个受热力学、动力学和生长条件影响的复杂过程。这些因素导致了单晶石墨烯岛形状的多样性。在这里，我们对使用低压CVD技术在铜外壳内表面上生长的不同形状的单晶石墨烯进行了实验性原子力显微镜（AFM）研究。最值得注意的是，这项研究表明，石墨烯单晶似乎形成在相邻的铜箔表面下方。在高度的横截面AFM扫描中揭示了该特征，这表明石墨烯表面位于相邻箔表面下方约15-30 nm。我们的研究结果还表明，杂质辅助生长机制通过各向同性扩散控制单晶石墨烯的生长，在所得薄片中产生二重、四重和六重对称性。此外，这里也存在通过各向异性扩散产生的单晶石墨烯，但它们没有表现出杂质辅助生长机制的迹象。最后，我们发现，在两重和四重对称的石墨烯结构通过各向同性扩散的应变弛豫比通过各向同性扩散的六重结构更复杂，这导致在低对称性结构中的多个步骤取向。
The chemical vapor deposition (CVD) growth of single-crystal graphene on polycrystalline copper foils is a complex process affected by thermodynamics, kinetics, and growth conditions. These factors lead to the diversity of island shapes of single crystal graphene. Here, we present an experimental atomic force microscopy (AFM) study of the different shapes of single-crystal graphene grown on the inner surface of copper enclosures using the low pressure CVD technique. Most remarkably, this study indicates that graphene single crystal appears to form below the adjacent copper foil surface. This feature is revealed in cross sectional AFM scans of the height, which indicate that the graphene surface lies below the neighboring foil surface by ∼15–30 nm. Our results also show that an impurity assisted growth mechanism governs the growth of single crystal graphene via isotropic diffusion, producing two-fold, four-fold, and six-fold symmetries in the resulting flakes. In addition, single crystal graphene produced via anisotropic diffusion is also present here, but they do not exhibit signs of an impurity assisted growth mechanism. Finally, we find that strain relaxation in two-fold and four-fold symmetric graphene structures via isotropic diffusion is more complicated than the six-fold structures via isotropic diffusion, which results in multiple steps orientations in low symmetry structures.