Highly conductive few-layer graphene/Al ₂O ₃ nanocomposites with tunable charge carrier type

An ex situ strategy for fabrication of graphene oxide (GO)/metal oxide hybrids without assistance of surfactant is introduced. Guided by this strategy, GO/Al ₂O ₃ hybrids are fabricated by two kinds of titration methods in which GO and Al ₂O ₃ colloids are utilized as titrant for hybrids of low and high GO content respectively. After sintered by spark plasma sintering, few-layer graphene (FG)/Al ₂O ₃ nanocomposites are obtained and GO is well reduced to FG simultaneously. A percolation threshold as low as 0.38 vol.% is achieved and the electrical conductivity surpasses 10 ³ Sm ^-1 when FG content is only 2.35 vol.% in FG/Al ₂O ₃ composite, revealing the homogeneous dispersion and high quality of as-prepared FG. Furthermore, it is found that the charge carrier type changes from p- to n-type as graphene content becomes higher. It is deduced that this conversion is related to the doping effect induced by Al ₂O ₃ matrix and is thickness-dependent with respect to FG.