Extended Data Fig. 1: In situ deposition of Cu particles on the graphite electrode for in situ sputter.
From: Cascaded compression of size distribution of nanopores in monolayer graphene
a, Schematic of electrode reactions and enhanced copper evaporation in the CVD chamber. The surface electrochemical reaction changes Cu to Cu(OH)2, which is very easy to evaporate. Then Cu(OH)2 particles would be reduced to Cu on the graphite electrode in the atmosphere of H2. b, A scanning electron microscopy image of the graphite electrode surface after Cu particle deposition. c, The corresponding energy-dispersive spectroscopy mapping of Cu of the graphite electrode in b. The red dots indicate the deposited Cu particles. Scale bars, 5 μm. d–f, Illustration of whether sputter-etching happens or not with different types of electrode: graphite (d), graphite deposited with Cu particles (e) and flat Cu covered by graphene film (f). g–i, The corresponding Raman spectrum of the graphene film after applying electric field with the anode materials shown in d–f. It proves that the in situ sputter results in the presence of exposed Cu particles at the anode. With more area of exposed Cu, the sputter effect would be stronger.
