Ni‐Catalyzed Graphitization of Diamond Nanostructures: A Pathway to Stable and Efficient Microplasma Cathodes

ABSTRACT The integration of conductive carbon phases with wide‐bandgap semiconductors is a promising route toward advanced optoelectronic applications. This study focuses on integrating formation of sp 2 carbon onto boron‐doped diamond nanostructures (GBDNS) through Ni‐catalyzed graphitization, aiming to develop efficient cathodes for microplasma illumination devices. The GBDNS architecture exhibits relatively a high electrical conductivity of 105.4 S·cm −1 with a carrier density of 1.8 × 10 20 cm −3 . Nickel acts as a nano‐mask during reactive ion etching, enabling the formation of boron‐doped diamond nanostructures. Upon high‐temperature annealing, Ni facilitates graphitization by catalyzing the transformation of sp 3 ‐bonded diamond surfaces into sp 2 ‐bonded graphite, evident through Structural and bonding analyses. Attributed to the formation of graphite on the nanostructures, BDNS 1000 cathode demonstrates significantly enhanced microplasma illumination performance, with a high plasma illumination current density of 7.3 mA·cm −2 , a low breakdown voltage of 330 V, and an extended lifetime stability of 848 min. The BDNS 1000 cathodes demonstrated excellent stability in a plasma environment, underscoring the advantage of combining nanostructuring and their graphitization sp 2 carbon architecture, which further provides efficient electron transport and surface stability. This study highlights a transfer‐free approach to engineering conductive sp 2 ‐graphitic networks on diamond, offering a robust platform for next‐generation microplasma and solid‐state optoelectronic devices.