Cu oxidation kinetics through graphene and its effect on the electrical properties of graphene

The oxidation kinetics of Cu through graphene were evaluated from the surface coverage of Cu oxide (F(ox)) by varying the oxidation time (t(ox) = 10–360 min) and temperature (T(ox) = 180–240 °C) under an air environment. F(ox), as a function of time, well followed the Johnson–Mehl–Avrami–Kolmogorov equation; thus, the activation energy of Cu oxidation was estimated as 1.5 eV. Transmission electron microscopy studies revealed that Cu(2)O formed on the top of the graphene at grain boundaries (G-GBs), indicating that Cu(2)O growth was governed by the out-diffusion of Cu through G-GBs. Further, the effect of Cu oxidation on graphene quality was investigated by measuring the electrical properties of graphene after transferring. The variation of the sheet resistance (R(s)) as a function of t(ox) at all T(ox) was converted into one curve as a function of F(ox). R(s) of 250 Ω sq(−1) was constant, similar to that of as-grown graphene up to F(ox) = 15%, and then increased with F(ox). The Hall measurement revealed that the carrier concentration remained constant in the entire range of F(ox), and R(s) was solely related to the decrease in the Hall mobility. The variation in Hall mobility was examined according to the graphene percolation probability model, simulating electrical conduction on G-GBs during Cu(2)O evolution. This model well explains the constant Hall mobility within F(ox) = 15% and drastic F(ox) degradation of 15–50% by the concept that the electrical conduction of graphene is disconnected by Cu(2)O formation along with the G-GBs. Therefore, we systematically developed the oxidation kinetics of Cu through graphene and simultaneously examined the changes in the electrical properties of graphene.