Characterization of the picosecond laser-ablated HOPG using Raman spectroscopy and SEM microscopy

Laser-based techniques for the production and modification of HOPG material are highly demanded in the production of functional surface micro/nanostructures required for various applications. A study on laser ablation of the HOPG using picosecond laser under specified laser and scanning parameters in ambient air to generate structured surfaces is reported in this work. The main objective was to establish the effects of laser fluence, scanning speed, hatching spacing, number of scanning passes and the position of the focal plane on the generation of the different types of micro/nanostructures on the HOPG surface after picosecond laser irradiation. The characteristics of the ablated surfaces of the HOPG formed during laser processing have been studied using Raman spectroscopy and scanning electron microscopy (SEM). Analysis of the Raman spectra indicated there are formations of Raman peaks with different sizes and intensities related to structural defects due to laser ablation. The SEM shows the appearances of laser-induced periodic surface structures (LIPSS) and different nano/microstructures after laser ablation depending on different levels of the parameters. The study shows that surface structures formed on the HOPG depend on the interaction of laser and scanning parameters. This work demonstrates that picosecond laser ablation of the HOPG is an important process that could be applied in different application areas such as nano/microstructures synthesis and thin-film deposition.