title: Near room temperature reduction of graphene oxide Langmuir-Blodgett monolayers by hydrogen plasma.
abstract: Langmuir-Blodgett monolayer sheets of graphene oxide (GO) were transferred onto Si and SiO2/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.
authors.affiliation: Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India. syed@iitb.ac.in.
authors.forename: Gulbagh
authors.initials: G
authors.lastname: Singh
authors.forename: V Divakar
authors.initials: VD
authors.lastname: Botcha
authors.forename: D S
authors.initials: DS
authors.lastname: Sutar
authors.forename: Pavan K
authors.initials: PK
authors.lastname: Narayanam
authors.forename: S S
authors.initials: SS
authors.lastname: Talwar
authors.forename: R S
authors.initials: RS
authors.lastname: Srinivasa
authors.forename: S S
authors.initials: SS
authors.lastname: Major