Laser-induced graphene (LIG) has drawn immense interest among researchers worldwide since its development in 2015. The laser writing strategy used to synthesize LIG is particularly advantageous, as it enables the direct patterning of graphene with micron-sized features. There have been many attempts to reduce the feature size of LIG in recent years, however, the studies have shown wide variations in the methods and findings. As such, this work presents a rigorous study on the irradiation of polyimide via an ultraviolet (355-nm) laser to realize micron-scale, high-quality LIG. Our work shows that there is often a tradeoff between micron-scale features and high-quality material, as the tightly focused beams that are demanded for small features are predisposed to ablation of the material. This work investigates such LIG synthesis by correlating the characteristics of the material, via scanning electron microscopy and Raman spectroscopy, to the optical fluence incident on the polyimide substrate, providing a measure of applied optical energy per unit area. The findings reveal that—given suitable attention to the optical fluence—high-quality LIG with Raman 2D-to-G peak height ratios approaching 0.7 can be synthesized with feature sizes down to 18 ± 2 μm. Furthermore, optical fluences between 40 to 50 J/cm2 produced the optimal LIG characteristics, as such optical fluences promote graphenization while minimizing ablation. The authors hope the findings of this study provide a foundation for the use of LIG in future integrated technologies.
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