a, Large-scale STM images of as-grown graphene films and after UHV-annealing at 250 °C, grown by ICP–CVD, and their related typical STS spectra. Insets are zoomed-in STM images, showing no periodic moiré pattern and no energy gap. b, Large-scale STM images of wrinkled graphene films grown by CVD under different bias voltages, and their related typical STS spectra. Inset is a zoomed-in STM image, showing moiré patterns with period of 5 nm and energy gap of 200–350 meV. c, Large-scale STM images of wrinkled graphene films after ICP post-treatment under different bias voltage, and their related typical STS spectra. Inset is zoomed-in STM image, showing no periodic moiré pattern and no energy gap. d, ARPES of ICP-CVD graphene films after UHV annealing at 500 °C, indicating the metastable state. e, Typical ARPES images extracted from different locations on the ICP post-treated graphene films on Cu(111). The doping is not homogeneous. f, The doping level changes gradually after UHV annealing, and the Dirac point will change from −120 meV (without annealing in e) to −170 meV (annealing at 200 °C) and finally reaches −320 meV (annealing at 400 °C). Scale bars in a–c are 4 nm, 6 nm and 4 nm, respectively. All the scale bars in the insets are 1 nm.