Nanocomposite and nanomaterials 

RF Plasma Reduction of Graphene Oxide
A. Nazarov1,2, O. Slobodian2, P. Okholin2, I. Tyagulskyy2, Yu.V. Gomeniuk2, O. Khyzhun3, A. Nikolenko2, S. Malyuta2, P. Lytvyn2, A. Rusavsky1,2, A. Vasin1,2, D. Savchenko1
1 National Technical University "Igor Sikorsky KPI", 37 Peremogy Pr., 03056 Kyiv, Ukraine. 
E-mail: nazarov@lab15.kiev.ua
2 V. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, 41 Nauky pr., 03680 Kyiv, Ukraine.
3 Frantsevych Institute for Problems of Materials Science NAS of Ukraine, 3 str. Krzhizhanovsky, 03142 Kyiv, Ukraine .

Reduced graphene oxide (r-GO) is very attractive 2D material for catalysis, chemical sensors, optical and photovoltaic component. Its properties is tuned broadly by changing of condition and regimes of reduction. In many cases low-temperature and fast time reduction of the GO is necessary component of device or material technology. In this work low-temperature RF (13.6 MHz) plasma treatment in forming gas (10%H2+90%N2) combined with low-temperature thermal annealing is suggested as effective fast method of GO reduction. Time of the plasma treatment is in the range from 5 to 15 sec. GO films were formed on Si and glass wafers by drop casting method. To clarify chemical structure of the film FTIR spectroscopy and XPS were used. Micro-Raman spectroscopy and AFM were applied to determine of structure and surface morphology correspondingly. The electrical properties of the films were studied by four-points method, I-V and I-T measurements. Mobility of charge carriers and type of conductivity were determined by Hall method.
It was shown that short RF plasma treatment (5-15 sec) results to strong cleaning of the GO from oxygen, and concentration ration of carbon to oxygen atoms reaches 4 while the thermal annealing at 200ºC for 15 min results only in 3.4. In the same time at RF plasma treatment in forming gas hydrogen and nitrogen are imbedded into carbon bonds that can be seen from FTIR spectra. Hall measurements show that after RF plasma treatment the GO films become doped by n-type with sheet resistance considerably smaller than thermal annealing at 250ºC for 15 min in vacuum. Resistance of the GO films after RF plasma annealing at 200ºC for 5 sec was on order of magnitude less than after thermal annealing in vacuum at 350ºC for 15 min. The nature of the phenomena is discussed.