Improving the conductivity of graphite-based films by rapid laser annealing

We present a method to anneal devices based on graphite films on paper and polycarbonate substrates. The devices are created using four different methods: spray-on films, graphite pencil-drawn films, liquid-phase exfoliated graphite films, and graphite powder abrasion-applied films. We characterize the optical properties of the films before and after laser annealing and report the two-terminal resistance of the devices for increased laser power density. We find the greatest improvement (16× reduction) in the resistance of spray-on film devices starting from 25.0 kΩ and reaching 1.6 kΩ at the highest annealing power densities. These improvements are attributed to local laser ablation of binders, stabilizers, and solvent residues left in the film after fabrication. This work highlights the utility of focused laser annealing for spray-on, drawn, printed, and abrasion fabricated films on substrates sensitive to heat/thermal treatments.