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Growth of umbrella-like millimeter-scale single-crystalline graphene on liquid copper

Zhang, Chitengfei, Tu, Rong, Dong, Mingdong, Li, Jun, Yang, Meijun, Li, Qizhong, Shi, Ji, Li, Haiwen, Ohmori, Hitoshi, Zhang, Song, Zhang, Lianmeng, Goto, Takashi
Carbon 2019 v.150 pp. 356-362
Raman spectroscopy, atmospheric pressure, copper, graphene, hydrogen, liquids, methane, scanning tunneling microscopy, transmission electron microscopy, vapors
Novel single-crystalline umbrella-like graphene (ULG) domains with the diameter up to 0.6 mm were achieved on liquid copper by atmospheric pressure chemical vapor deposition (APCVD). ULG exhibits 6-fold symmetry with 6 ribs. Raman spectroscopy analysis revealed that the ULG was few-layer graphene with ultralow level of defects. Scanning Tunneling Microscope (STM) and selected area electron diffraction (SAED) results shown the single-crystalline nature of ULG. Transmission electron microscopy (TEM) shown the thickness of the panel was 3.5 nm and the thickness of the rib varied gradiently from 11.22 nm to 5.44 nm. The growth mechanism of the ULG was also explored by studying the influence of varied methane and hydrogen flow, which shows the ULG was formed during the nucleation stage. The larger flow of hydrogen supported decreasing the nucleation density of ULG, which was preferred for the formation of large domain ULG. Moreover, ULG partially immersed into liquid copper during the nucleation stage, thus, carbon atoms could reach each layer of ULG, leading to the continual growth of ULG graphene.