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 sp2 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<middle dot>cm-1 with a carrier density of 1.8 x 1020 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 sp3-bonded diamond surfaces into sp2-bonded graphite, evident through Structural and bonding analyses. Attributed to the formation of graphite on the nanostructures, BDNS1000 cathode demonstrates significantly enhanced microplasma illumination performance, with a high plasma illumination current density of 7.3 mA<middle dot>cm-2, a low breakdown voltage of 330 V, and an extended lifetime stability of 848 min. The BDNS1000 cathodes demonstrated excellent stability in a plasma environment, underscoring the advantage of combining nanostructuring and their graphitization sp2 carbon architecture, which further provides efficient electron transport and surface stability. This study highlights a transfer-free approach to engineering conductive sp2-graphitic networks on diamond, offering a robust platform for next-generation microplasma and solid-state optoelectronic devices.