Electron mobility modulation in graphene oxide by controlling carbon melt lifetime

The lack of bandgap is a fundamental issue in graphene devices, which can be solved by fabricating reduced graphene oxide (rGO). However, its device integration is impeded by the elevated reduction temperature (>2000 K) requirements. Recently, we demonstrated a new approach for laser writing heavily-reduced GO by employing the nonequilibrium approach of nanosecond laser annealing (Gupta and Narayan, 2019) [1]. Here, we report on the electron mobility modulation in the liquid phase grown graphene oxide. The process involves melting and subsequent quenching of molten carbon, which triggers the first-order phase transformation of amorphous carbon (a-C) into rGO. Laser annealing at energy density above the 0.3 J/cm(2) melting threshold results in liquid-phase rGO growth on Si/SiO2. The rGO films exhibit 26 cm(2)/V-s room-temperature electron mobility and -4.7 x 10(21)/cc charge carrier concentration on annealing near melt threshold. The heavily-reduced GO films are formed on -O- creeping in the loosely-packed low undercooled carbon melt during ultrafast quenching. We establish that -O- injection is an implicit function of melt lifetime, and a rise in melt lifetime triggers GO film regrowth with increased mobility >210 cm(2)/V-s and 2.2 x 10(19)/cc carrier concentration on annealing at 0.6 J/cm(2). Laser annealing resolves the fundamental issues of impurities and topological defects in rGO fabrication by equilibrium-based methods, facilitating increased electron mobility in laser patterned graphene-based materials. (C) 2020 Elsevier Ltd. All rights reserved.