Near room temperature reduction of graphene oxide Langmuir-Blodgett monolayers by hydrogen plasma

Langmuir-Blodgett monolayer sheets of graphene oxide (GO) were transferred onto Si and SiO 2 /Si, and subjected to hydrogen plasma treatment near room temperature. GO monolayers were morphologically stable at low power (15 W) plasma treatment, for durations up to 2 min and temperatures up to 120 °C. GO monolayers reduced under optimized plasma treatment conditions (30 s duration at 50 °C) exhibit a sheet thickness of (0.5-0.6) nm, high sp 2 -C content (75%), a low O/C ratio (0.16) and a significant red-shift of Raman G-mode to 1588 cm −1 , indicating efficient de-oxygenation and a substantial decrease of defects. A study of the valence band electronic structure of hydrogen plasma reduced GO monolayers shows an increase of DOS in the vicinity of the Fermi level, due to the increase of C 2p-π states, and a substantial decrease of work function. These results, along with conductivity measurements and transfer characteristics, reveal the p-type nature of hydrogen plasma reduced GO monolayers, displaying a conductivity of (0.2-31) S cm −1 and a field effect mobility of (0.1-6) cm 2 V −1 s −1 . Plasma treatment at higher temperatures results in a substantial increase in sp 3 -C/damaged alternant hydrocarbon content and incorporation of defects related to the hydrogenation of the graphitic network, as evidenced by multiple Raman features, including a large red-shift of D-mode to 1331 cm −1 and a high I (D)/ I (G) ratio, and supported by the appearance of mid-gap states in the vicinity of the Fermi level. A comprehensive investigation of the morphological stability, chemical and electronic structure of hydrogen plasma reduced GO Langmuir-Blodgett monolayers, under different conditions of plasma treatment (power, duration and temperature).