Enhanced Field Electron Emission and Plasma Illumination Performance of Flexible Laser-Induced Graphene-Boron-Doped Diamond Nanowall Hybrid Nanostructures

This study demonstrates a scalable fabrication method for flexible laser-induced graphene (LIG)-boron doped diamond nanowall (BDNW) hybrid nanostructures. Direct laser writing on polyimide film is enhanced in the presence of BDNW powder fabricated by chemical vapor deposition (CVD), where the appreciable absorbance of BDNWs at the CO₂ laser wavelength increases the local film temperature. Furthermore, thanks to superior thermal conductivity and heat capacity of BDNWs, more uniform heat distribution and longer lasting thermal shock is possible during lasing process of polyimide film decorated with BDNW. In addition to graphene formation, the thermal shock due to laser irradiation produces graphitized and amorphous carbon at the diamond grain boundaries, increasing the thermal and charge transfer capacity at the LIG-diamond interfaces. Developing flexible and robust field electron emission (FEE) cathode materials with long-lasting stability is crucial for electronic devices that rely on plasma illumination (PI). A promising strategy to achieve this goal is utilizing hybrid nanomaterials based on conductive diamond nanostructures. In this work, a two-step technique was employed to fabricate hybrid nanostructures of boron-doped diamond nanowalls by LIG on flexible polyimide foils. The obtained results revealed that the presence of BDNW increased the defect density in the LIG while significantly enhancing the electrical conductivity simultaneously. It was found that the PI properties of BDNW/LIG hybrid nanostructures, when utilized as a cathode in a PI device, were superior compared to those of neat LIG. The breakdown voltages of BDNW/LIG hybrids were lower than LIG, i.e., 320 versus 350 V. Moreover, the current density (J_PI) was higher for BDNW/LIG hybrids, reaching 9.48 mA/cm² at an applied voltage of 600 V. The rate of J_PIenhancement with applied voltage was much higher for BDNW/LIG hybrids. Additionally, it was observed that upon BDNW incorporation, the lifetime stability of LIG cathodes was enhanced almost twice.