Issue 23, 2014

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 sp2-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) cm2 V−1 s−1. Plasma treatment at higher temperatures results in a substantial increase in sp3-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.

Graphical abstract: Near room temperature reduction of graphene oxide Langmuir–Blodgett monolayers by hydrogen plasma

Article information

Article type
Paper
Submitted
28 Feb 2014
Accepted
16 Apr 2014
First published
17 Apr 2014

Phys. Chem. Chem. Phys., 2014,16, 11708-11718

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

G. Singh, V. D. Botcha, D. S. Sutar, P. K. Narayanam, S. S. Talwar, R. S. Srinivasa and S. S. Major, Phys. Chem. Chem. Phys., 2014, 16, 11708 DOI: 10.1039/C4CP00875H

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