Highly Conductive Few-Layer Graphene/Al2O3 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/Al2O3 hybrids are fabricated by two kinds of titration methods in which GO and Al2O3 colloids are utilized as titrant for hybrids of low and high GO content respectively. After sintered by spark plasma sintering, few-layer graphene (FG)/Al2O3 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 103 Sm-1 when FG content is only 2.35 vol.% in FG/Al2O3 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 Al2O3 matrix and is thickness-dependent with respect to FG.