Synergistic Role of Electron and Photon Doses in Stepwise Laser-Induced Complete Deoxygenation of Graphene Oxide Revealed by In-Situ TEM

Laser-induced reduction of graphene oxide (GO) is a highly promising route to graphene synthesis, offering spatially localized processing, elimination of hazardous chemical reagents, and compatibility with ambient conditions. Here, we introduce a stepwise laser reduction strategy employing a 532 nm pulsed laser and a 200 keV electron beam for irradiation in a transmission electron microscope. By systematically varying the pulse sequence and the cumulative photon and electron doses, complete deoxygenation of GO is achieved while preserving film integrity. Core-loss EELS confirms full removal of oxygen functional groups and restoration of the sp2 graphitic network, evidenced by a π*−σ* energy separation of 7.0 eV, in close agreement with graphite (7.1 eV). Crucially, the cumulative electron dose is identified as an active parameter governing the reduction mechanism. While electron beam exposure accounts for only 5 at. % of the initial oxygen removal, tracking the oxygen removal kinetics finds that it synergistically lowers the energy barrier for subsequent laser-driven deoxygenation. However, excessive electron exposure is found to compromise film integrity through crack formation. The optimal configuration achieves complete deoxygenation at a cumulative photon dose of 2.5 × 103 mJ/cm2 with superior in-plane crystallographic order and minimal beam-induced thinning. This electron-beam-assisted photoreduction strategy provides a route toward controlled, atomic-scale patterning of GO for advanced device fabrication.