Flexible Cold Cathodes Based on Graphite Nanoplatelet Coatings on Silicone Rubber

We report the fabrication and characterization of flexible cold cathodes based on graphite nanoplatelet (GNP) coatings on silicone rubber substrates. GNPs, synthesized via thermal exfoliation of graphite bisulfate and sonication in acetone, form nanostructured coatings with controlled roughness and thickness. Morphological, structural, and spectroscopic analyses confirm the presence of crystalline, few-layer graphitic domains. Field emission was locally probed by using a nanomanipulated tungsten tip anode inside a scanning electron microscope, revealing a turn-on voltage as low as 8.2 V and a field enhancement factor ~80 at an anode-cathode distance of 100 nm. Emission characteristics are measured in different substrate curvature configurations: sharper bending alters the exposure of nanoplatelet edges, influencing the turn-on voltage and the field enhancement factor. The emitters exhibit excellent stability, robustness under strain, and thermally activated conduction behaviour with activation energy of ~0.31 eV. Our findings demonstrate that GNP-coated silicone rubbers are a scalable, low-cost, and mechanically adaptive platform for next-generation vacuum microelectronics, enabling flexible, high-performance electron sources with nanoscale control and real-time tunability.