Investigating the ablation threshold and morphology of spots generated on graphite electrode by femtosecond Gaussian laser pulses

Abstract

This study investigates the effects of femtosecond laser irradiation on graphite, a highly sought-after material known for its exceptional chemical stability and ability to withstand extreme temperatures. The ablation threshold and surface morphology of graphite were determined using a tightly focused laser beam with varying pulse numbers and laser fluences. The results showed that the laser beam produced diverse morphological structures within different regions of a single laser spot, and the ablation threshold and surface morphology were significantly influenced by the number of pulses and the energy density of the incident laser. The study found that the ablation threshold of graphite was 107, 90, 76, and 56 ± 0.5 mJ/cm2 for 5, 50, 200, and 500 laser pulses, respectively. The resulting surface structures ranged from quasi-periodic to periodic, with varying periodicities, and the ablation debris exhibited morphologies from fine particles to long filaments. The crystal structure of the specimen was analyzed via X-ray diffraction and micro-Raman spectroscopy, with compositional analysis performed using energy-dispersive X-ray spectroscopy (EDX). Notably, a significant broadening of the Raman spectrum peaks with increasing pulse energy suggested the formation of a more disordered structure. These findings demonstrate that femtosecond laser ablation can precisely manipulate the surface morphology and nanoparticle production, presenting potential applications in fields such as nanoparticle generation and engineering surface properties like adhesion, biocompatibility, spectral reflectivity, wear resistance, and wettability.