Comparison between filamentary and diffuse dielectric barrier discharges at atmospheric pressure for the treatment of monolayer graphene films

Abstract This work compares the treatment of monolayer graphene films by either diffuse or filamentary dielectric barrier discharge (DBD) operated in N 2 at atmospheric pressure. To control the discharge regime, the 1 kHz sinusoidal voltage waveform used for diffuse discharge formation is shifted to a square voltage waveform, while keeping all other parameters constant. Polycrystalline graphene films are first grown by chemical vapor deposition (CVD) and then exposed to the DBD for up to 30 000 cycles of the applied voltage (total treatment time of 30 s). Plasma-induced disordering is investigated by Hyperspectral Raman imaging. In the diffuse discharge regime, a progressive rise in defect density is observed with increasing treatment times, with a transition towards amorphous carbon after 30 s. However, graphene maintains its CVD growth structure with the presence of grain boundaries (GBs). For short treatment times in the filamentary discharge regime, the highly localized energy transfers associated to the microdischarges lead to circular defective areas. The diameter of typical damaged zones from Raman imaging is ∼ 40 μ m , while the diameter of the zone in which carbon atoms are clearly removed, as seen in atomic force microscopy, is only ∼ 2 μ m . After 30 s, an amorphous carbon sheet is formed with no evidence of GBs remaining after treatment.