Ultrafast laser ablation of graphite

Atomic force microscopy and Raman scattering studies of femtosecond laser-induced nanohillocks on CR-39

“…In another example ultrafast melting of graphite is observed by Raman spectroscopy, atomic force microscopy as well as time of flight mass spectrometry. A displacive motion between the topmost surface layers is attributed to Coulomb explosion [21]. Recently the identification of the unique appearance of individual, localized nanohillocks, typically a few nm in height and with a few tens of nm in diameter after interaction of ultra-short laser radiation with surfaces of metals, dielectrics and semiconductors are regarded as characteristic for a strong localized potential energy deposition to the electronic system resulting in Coulomb explosion [22].…”

Laser induced non-thermal deposition of ultrathin graphite

“…1(b) and 1(c)). 13,16 At high fluences above 450 mJ/cm 2 , the SEM image ( Fig. 1(c)) of the ablation crater on the HOPG surface shows two regions and almost no ablative debris is observed.…”

“…Using the example of graphite, we show the consistence of experimental and calculated thermal and non-thermal ablation thresholds of this layered material. 16,17 Moreover, the laser induced transfer of intact ultrathin graphite layers from a HOPG target onto a transparent substrate is realized. Raman spectroscopy measurements are carried out, proving the characteristic sp 2 structure of the graphite layers is maintained during the ablation process.…”

“…Assuming the ablation model, 10 which is based on momentum transfer in direction normal to the surface between oscillating graphite layers, this is an expected consequence of the delayed electron-phonon interaction occurring after 500 fs. 16,18,19 A potential explanation for the offset deviation of approximately 200 mJ/cm 2 between the theoretical and the experimental thresholds might be the consideration of grain size of HOPG targets of different grade, enforcing the necessity of breaking numerous high energetic covalent bonds at the edges of the ablated graphitic flakes in those cases where the grain size exceeds the focus diameter. This scenario would be comparable with the theoretical ablation threshold, which is calculated on the basis of the absorption of homogenous single crystalline layers neglecting grain boundaries in polycrystalline structures.…”

Transforming graphite to nanoscale diamonds by a femtosecond laser pulse

“…9 It has also been suggested that hexagonal diamond can be created by laser-irradiation of highly oriented pyrolytic graphite (HOPG). 10 12 Liu et al have reported a laser-based method to write diamond patterns on graphite with lm precision.…”