Confocal Microscopy for in Situ Multi‐Modal Characterization and Patterning of Laser‐Reduced Graphene Oxide

Graphene oxide (GO) films can be readily prepared at wafer scale, then reduced to form graphene-based conductive circuits relevant to a range of practical device applications. Among a variety of reduction methods, laser processing has emerged as an important technique for localized reduction and patterning of GO films. In this study, the novel use of confocal microscopy is demonstrated for high-resolution characterization, in situ laser reduction, and versatile patterning of GO films. Multi-modal imaging and real-time tracking are performed with 405 and 488 nm lasers, enabling large-area direct observation of the reduction progress. Using image analysis to cluster flake types, the different stages of reduction can be attributed to thermal transfer and accumulation. Delicate control of the reduction process over multiple length scales is illustrated using millimeter-scale stitched patterns, micropatterning of single flakes, and direct writing conductive 2D wires with sub-micrometer resolution (530 nm). The general applicability of the technique is shown, allowing fabrication of both conductive reduced graphene oxide (rGO) films (sheet resistance: 2.5 kOhm sq(-1)) and 3D microscale architectures. This simple and mask-free method provides a valuable tool for well-controlled and scalable fabrication of reduced GO structures using compact low-power lasers (< 5 mW), with simultaneous in situ monitoring and quality control.