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 heav...

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Bibliographic Details
Published in:Carbon (New York) 2020-12, Vol.170, p.327-337
Main Authors: Gupta, Siddharth, Joshi, Pratik, Narayan, Jagdish
Format: Article
Language:English
Subjects:
Additive manufacturing
Annealing
Band gap
Carbon
Carrier density
Creep (materials)
Current carriers
Defect annealing
Electron mobility
Electrons
Equilibrium methods
Flux density
Graphene
Laser annealing
Laser beam annealing
Liquid phases
Mobility
Modulation
Molten carbon
Phase transitions
Quenching
Raman spectroscopy
Room temperature
Silicon dioxide
Transmission electron microscopy
Undercooling
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Summary: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/cm2 melting threshold results in liquid-phase rGO growth on Si/SiO2. The rGO films exhibit 26 cm2/V-s room-temperature electron mobility and −4.7 × 1021/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 cm2/V-s and 2.2 × 1019/cc carrier concentration on annealing at 0.6 J/cm2. 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. [Display omitted]
ISSN:0008-6223
1873-3891
DOI:10.1016/j.carbon.2020.07.073