Identification of Semiconductive Patches in Thermally Processed Monolayer Oxo-Functionalized Graphene

The thermal decomposition of graphene oxide (GO) is a complex process at the atomic level and not fully understood. Here, a subclass of GO, oxo-functionalized graphene (oxo-G), was used to study its thermal disproportionation. We present the impact of annealing on the electronic properties of a monolayer oxo-G flake and correlated the chemical composition and topography corrugation by two-probe transport measurements, XPS, TEM, FTIR and STM. Surprisingly, we found that oxo-G, processed at 300 °C, displays C−C sp³-patches and possibly C−O−C bonds, next to graphene domains and holes. It is striking that those C−O−C/C−C sp³-separated sp²-patches a few nanometers in diameter possess semiconducting properties with a band gap of about 0.4 eV. We propose that sp³-patches confine conjugated sp²-C atoms, which leads to the local semiconductor properties. Accordingly, graphene with sp³-C in double layer areas is a potential class of semiconductors and a potential target for future chemical modifications.