Low-resistance laser-induced graphitic carbon by maximizing energy delivery and pulse overlap

Laser-induced graphitic carbon (LIGC) is a promising technology to manufacture conductive carbon in a cost-effective manner on a flexible substrate with a scanned laser. One limitation preventing the widespread adoption of LIGC in electronic devices and circuits has been its relatively high sheet resistance. Here, we report the lowest sheet resistance to date for LIGC engraved on flexible polyimide of 6.14 ± 0.11 Ω/□. Several general strategies are identified to minimize sheet resistance. Most importantly, the total laser energy per unit area delivered to the substrate needs to be maximized. This can be achieved by increasing laser power, decreasing laser scan speed and increasing overlap between adjacent pulses. Pulse overlap can be increased by increasing linewidth (raster rather than vector mode) and increasing the dots per cm resolution, i.e., decreasing spacing between pulses, which also improves LIGC uniformity. Further, decreasing scan speed increases the ablation threshold because of increased cooling between pulses enabling more energy to be delivered without the material ablating. These insights were obtained using a combination of electrical measurements, thermal modeling and material characterization. With optimized energy delivery, a domain size (La) of about 60 nm was obtained, which highlights the high quality of the obtained LIGC material. [Display omitted]