Laser direct writing offers precise material treatment with minimal thermal damage, crucial for controlled energy application, beam-material interaction, and heat penetration. Traditional methods for large-area graphene growth, such as chemical vapor deposition (CVD), typically require metallic precursors like Cu and Ni. However, recent advancements have demonstrated the potential for non-metallic precursors. Notably, Rice University showed that CO2 laser irradiation could convert polyimide (PI) and polyetherimide (PEI) into graphene. In this study, we present a laser direct writing technique for forming graphene patterns on polybenzimidazole (PBI) thin films and glass substrates using a low-cost nanosecond UV laser system. This method avoids thermal damage to substrates and eliminates the need for metallic precursors. The UV laser induces photochemical reactions, breaking molecular bonds to form graphene without harming the substrate.

The methodology involves dissolving PBI in dimethylacetamide (DMAC) to create a solution, which is then coated on glass sheets. After drying the coated glass, a nanosecond UV laser is used to treat the PBI-coated sheet, forming flaky silver-black graphene. Optimal laser conditions include a wavelength of 355 nm, a pulse duration of 100 ns, a frequency of 50 kHz, and a scanning speed of 20 mm/s. A Q factor of around 16.4 yields the best results, producing graphene with a resistance of approximately 50Ω over 2 mm.

Raman spectroscopy confirms the graphene formation, indicated by the characteristic 2D peak and the D/G peak ratio, which reflects the degree of carbon crystallization and defect ratio.

In conclusion, this cost-effective nanosecond UV laser technique offers a scalable approach to graphene production on PBI films and glass substrates, presenting a significant advancement in non-thermal, metal-free graphene fabrication.