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Localized voltage-induced reduction, initiated by a conductive atomic force microscope probe under ambient conditions, is used to pattern electrically conductive reduced graphene oxide (rGO) regions in electrically insulating graphene oxide (GO). This method is shown to reduce single and multiple layer GO on ultra-flat Au substrates with feature sizes as small as 4.0 nm, with the reduction resolution depending strongly on humidity and number of GO layers. In situ current levels during reduction are used to track reaction kinetics, which follow a rate-limited process where the generation and transport of hydrogen ions are the primary rate limiting steps. Tip-enhanced Raman spectroscopy is used to map the nanoscale structure and local disorder in voltage-reduced GO and rGO single sheets. It is found that reduction of GO causes a decrease in tip-enhanced Raman scattering intensity in both the D-band and Gband, but the D/G intensity ratio remains unchanged following reduction, indicating that defects are not introduced by the reduction process.

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Graphene oxide (GO) has garnered attention for its tunable chemical, electrical, and optical properties. An integral part of the efforts to manipulate and improve the performance of GO is the ability to reliably characterize its complex structure. Raman spectroscopy and confocal Raman mapping are widely used for insight into the extent of GO's nanoscale graphene-like domains, the degree of lattice order, and its sheet stacking structure. It has also been reported, however, that laser sources, similar to those used for Raman spectroscopy, can be used to intentionally reduce and ablate GO. In light of this, it is unclear how invasive Raman measurements of GO are and how reliable published Raman data is. In this study, we employ Raman laser doses spanning 4 orders of magnitude to investigate the impact of Raman measurements on GO structure. We find that GO undergoes reduction at all practical laser doses, with the degree of reduction increasing with dose. Lattice damage and ablation dominate at high laser doses. Based on our findings, we encourage the use of a minimal laser dose (8 × 10 7 J/m 2 or below) for Raman measurements of GO. Despite the resulting loss in signal, these conditions limit sample modification and measurement inaccuracies.

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