Two-Beam Ultrafast Laser Scribing of Graphene Patterns with 90-nm Subdiffraction Feature Size

Abstract

The fabrication of high-resolution laser-scribed graphene devices is crucial to achieving large surface areas and thus performance breakthroughs. However, since the investigation mainly focuses on the laser-induced reduction of graphene oxide, the single-beam scribing provides a tremendous challenge to realizing subdiffraction features of graphene patterns. Here, we present an innovative 2-beam laser scribing pathway for the fabrication of subdiffraction graphene patterns. First, an oxidation reaction of highly reduced graphene oxide can be controllably driven by irradiation of a 532-nm femtosecond laser beam. Based on the oxidation mechanism, a 2-beam laser scribing was performed on graphene oxide thin films, in which a doughnut-shaped 375-nm beam reduces graphene oxide and a spherical 532-nm ultrafast beam induces the oxidation of laser-reduced graphene oxide. The spherical beam turns the highly reduced graphene oxide (reduced by the doughnut-shaped beam) to an oxidized state, splitting the laser-scribed graphene oxide line into 2 subdiffraction featured segments and thus forming a laser-scribed graphene/oxidized laser-scribed graphene/laser-scribed graphene line. Through the adjustment of the oxidation beam power, the minimum linewidth of laser-scribed graphene was measured to be 90 nm. Next, we fabricated patterned supercapacitor electrodes containing parallel laser-scribed graphene lines with subdiffraction widths and spacings. An outstanding gravimetric capacitance of 308 F/g, which is substantially higher than those of reported graphene-based supercapacitors, has been delivered. The results offer a broadly accessible strategy for the fabrication of high-performance graphene-based devices including high-capacity energy storage, high-resolution holograms, high-sensitivity sensors, triboelectric nanogenerators with high power densities, and artificial intelligence devices with high neuron densities.