Yao Wenqian, Zhang Jianing, Ji Jie, Yang He, Zhou Binbin, Chen Xin, Bøggild Peter, Jepsen Peter U, Tang Jilin, Wang Fuyi, Zhang Li, Liu Jiahui, Wu Bin, Dong Jichen, Liu Yunqi
Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Beijing, 100190, P. R. China.
Sino-Danish Center for Education and Research, Sino-Danish College, University of Chinese Academy of Sciences, Beijing, 100049, China.
Adv Mater. 2022 Feb;34(8):e2108608. doi: 10.1002/adma.202108608. Epub 2021 Dec 29.
Synthesis of large-scale single-crystalline graphene monolayers without multilayers involves the fabrication of proper single-crystalline substrates and the ubiquitous formation of multilayered graphene islands during chemical vapor deposition. Here, a method of cyclic electrochemical polishing combined with thermal annealing, which allows the conversion of commercial polycrystalline Cu foils to single-crystal Cu(111) with an almost 100% yield, is presented. A global "bottom-up-etching" method that is capable of fabricating large-area pure single-crystalline graphene monolayers without multilayers through selectively etching bottom multilayered graphene underneath large area as-grown graphene monolayer on Cu(111) surface is demonstrated. Terahertz time-domain spectroscopy (THz-TDS) measurement of the pure monolayer graphene film shows a high average sheet conductivity of 2.8 mS and mean carrier mobility of 6903 cm V s over a large area. Density functional theory (DFT) calculations show that the selective etching is induced by the much easier diffusion of hydrogen atoms than hydrocarbon radicals across the edges of the top graphene layer, and the simulated selective etching processes based on phase field modeling are well consistent with experimental observations. This work provides new ways toward the production of single-crystal Cu(111) and the synthesis of pure monolayer graphene with high electronic quality.
合成无多层的大规模单晶石墨烯单层涉及制备合适的单晶衬底以及在化学气相沉积过程中普遍形成多层石墨烯岛。在此，提出了一种循环电化学抛光与热退火相结合的方法，该方法能够以近100%的产率将商业多晶铜箔转化为单晶Cu(111)。展示了一种全局“自下而上蚀刻”方法，该方法能够通过选择性蚀刻Cu(111)表面大面积生长的石墨烯单层下方的底部多层石墨烯来制备无多层的大面积纯单晶石墨烯单层。对纯单层石墨烯薄膜的太赫兹时域光谱(THz-TDS)测量显示，在大面积上具有2.8 mS的高平均面电导率和6903 cm² V⁻¹ s⁻¹的平均载流子迁移率。密度泛函理论(DFT)计算表明，选择性蚀刻是由氢原子比烃基更容易在顶部石墨烯层边缘扩散引起的，基于相场建模的模拟选择性蚀刻过程与实验观察结果高度一致。这项工作为生产单晶Cu(111)和合成具有高电子质量的纯单层石墨烯提供了新途径。
