The effect of heat treatment on formation of graphene thin films from graphene oxide nanosheets

Graphene thin films with very low concentration of oxygen-containing functional groups were produced by reduction of graphene oxide nanosheets (prepared by using a chemical exfoliation) in a reducing environment and using two different heat treatment procedures (called one and two-step heat treatment procedures). The effects of heat treatment procedure and temperature on thickness variation of graphene platelets and also on reduction of the oxygen-containing functional groups of the graphene oxide nanosheets were studied by atomic force microscopy and X-ray photoelectron spectroscopy. While formation of the thin films composed of single-layer graphene nanosheets with minimum thickness of 0.37 nm and nearly without any functional group bonds was observed at the high temperature of 1000 degrees C in the one-step reducing procedure, similar high quality graphene thin films were obtained at the lower temperature of 500 degrees C in our two-step reducing temperature. The results also indicated possibility of efficient reduction of the graphene oxide thin films at even lower heat treatment temperatures (<= 500 degrees C). (c) 2009 Elsevier Ltd. All rights reserved.