Effect of ambient air on femtosecond laser ablation of highly oriented pyrolytic graphite

Abstract

Highly oriented pyrolytic graphite is ablated by femtosecond laser in air and vacuum, respectively. The morphologies and material components of the ablated target surface are examined by scanning electron microscopy and micro-Raman spectroscopy. For laser fluence no less than 0.5 J/cm(2), the laser-induced periodic surface grooves formed in air are found to be much less clearer than those formed in vacuum; beneath the amorphous carbon debris, the surface ablated in air is composed of nanocrystalline graphite, but in vacuum it retains the ordered graphite structure. The thermal relaxation of the ablated target induced by air-assisted heat transfer is considered to be the main reason for the differences. The transportation of air molecules along the surface, the classical size effect of heat conduction and high solid-air heat transfer coefficient in nanoscale enhance the air-assisted heat transfer.

Large-area fabrication of low- and high-spatial-frequency laser-induced periodic surface structures on carbon fibers

“…3b), which exhibit a relatively weak surface modulation with 10 a spatial period Λ = (872  62 nm). Analogue to HSFL and in good agreement to literature [29,33], the orientation of LSFL is also perpendicular to the linear beam polarization. For F < 1.6 J/cm 2 (not shown here), the possible transition between HSFL and LSFL was not observed because of the insufficient number of laser pulses.…”

“…While the LIPSS formation on graphite was studied by several groups in dependence on different influencing parameters (beam polarization, laser peak fluence) on the flat surface of bulk materials [28][29][30][31][32], the formation of LIPSS on the surface of carbon fibers is less investigated [11,33]. By performing single-spot experiments on strongly curved fiber surfaces, Sajzew et al [33] demonstrated the formation of LSFL and HSFL within the Gaussian intensity 4 distribution of the focal spot (diameter 50 µm) upon the irradiation of N = 50 linearly polarized fs-laser pulses with a peak fluence F = 4 J/cm 2 .…”

Femtosecond laser patterning of graphene electrodes for thin-film transistors

“…Femtosecond laser patterning of CVD-grown graphene electrodes on silicon substrates and their application as source and drain electrodes in MOTFTs were studied. The quality of the patterned electrodes was improved by laserablation in vacuum due to debris reduction compared to laser processing in air which is consistent with previous reports on laser processing in vacuum [28][29][30]. Raman spectroscopy analysis showed that the I(2D)/I(G) ratios for samples processed in air and in vacuum (≈ 2) are comparable, which suggests that having air or vacuum as environment during patterning does not considerably influence the graphene layer.…”

“…The problem however is that during laser patterning graphene forms folds [27] and debris causing disturbance resulting in unwanted defects and negative impact on its application as transistor electrodes. Femtosecond laser ablation of graphene in vacuum, compared to air, should result in cleaner and more controlled patterning of the layer because rather less material is redeposited on the substrate [28][29][30]. Moreover, atmospheric oxygen can oxidize the remaining graphene upon laser ablation and reduce performance of graphenebased electronics.…”

Graphene Fabrication by Using Femtosecond Pulsed Laser and Its Application on Passively Q-Switched Solid-State Laser as Saturable Absorber

“…2(a). Different from that of the HOPG, the D band at about 1350 cm −1 appears in the Raman spectrum of the laser-exfoliated graphene, moreover, the D-band and G-band are broadened, which indicate that the exfoliated graphene was in a few-layers form [32].…”