Heterogeneous surface recombination of oxygen atoms on vertically oriented multilayer graphene sheets deposited on a metal substrate

• Propane plasma with a power density of 2 kW/L was used for nanocarbon deposition. • Carbon nanowalls grew at the deposition rate of ∼ 100 nm/s. • The recombination coefficient for oxygen atoms was measured for various morphologies. • The recombination coefficient was between 0.01 and 0.65, depending on morphology. • A deep minimum was explained by two contradictory effects: surface coverage with carbon and thickness of the layer of deposited nanomaterials. The kinetics of surface recombination of neutral oxygen atoms on nanocarbon deposited on oxidized cobalt catalyst in inductively coupled radiofrequency plasma sustained in propane in the H-mode is presented. The coefficient was measured in the range of temperatures between 300 and 800 K and pressures between 40 and 200 Pa. A deep minimum in the coefficient at 0.03 – 0.06 was observed and explained by a deposition of a rather smooth carbon film on the cobalt catalyst. Prolonged deposition caused the growth of perpendicularly oriented multilayer graphene sheets with the distance between the neighboring sheets around 100 nm. The large aspect ratio of the gaps, whose depth reached several micrometers after deposition time over 100 s, caused the trapping of oxygen atoms and, thus, numerous collisions with the graphene-like surface, so the coefficient increased for over an order of magnitude. The maximum coefficient over 0.5 was observed at low pressures and elevated temperatures. The evolution of the recombination coefficient was explained by the peculiarities of the binding sites for oxygen atoms on graphene surfaces.