Abstract:The effect of a nanosecond laser irradiation of thin (60 and 145 nm) amorphous, diamond-like carbon films deposited on Si substrate by an ion beam deposition (IBD) from pure acetylene and acetylene/hydrogen (1:2) gas mixture was analyzed in this work. The films were irradiated with the infrared (IR) and ultraviolet (UV) radiation of the nanosecond Nd:YAG lasers working at the first (1.16 eV) and the third (3.48 eV) harmonics, using a multi-shot regime. The IR laser irradiation stimulated a minor increase in the fraction of sp 2 bonds, causing a slight decrease in the hardness of the films and initiated SiC formation. Irradiation with the UV laser caused the formation of carbides and increased hydrogenization of the Si substrate and the fraction of sp 2 sites. Spalliation and ablation were observed at a higher energy density and with a large number of laser pulses per spot.

Coherent laser irradiation of amorphous carbon films formed on Si substrates by ion beam deposition from pure acetylene and acetylene/hydrogen gas mixture is analyzed in this work. The films were irradiated with nanosecond YAG:Nd laser (Ekspla NL301G) at the first (1064 nm, 6 ns), the second (532 nm, 4.2 ns) and the third (355 nm, 28 ns) harmonic by scanning or repeating (10 pulses to one point) regime. Irradiation by the first laser harmonic leads to a minor increase of graphite phase content and shows SiC formation. Formation of carbides was observed at the second harmonic irradiation when irradiation intensity is low (< 10 MW/cm 2 ). Graphitization became more intensive when power density of irradiation increased and the films transformed to the glass carbon and nano/micro crystallite compound at intensive ablation regime (≈ 24 MW/cm 2 ). Early ablation starts at irradiation by the third laser harmonic with the intensity of ≈ 8 MW/cm 2 with an increase of Si substrate roughness. Swelling of films was obtained when the sample was irradiated at the third harmonic with 1 MW/cm 2 .

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Amorphous hydrogenated carbon lms were formed on the Si (100) wafers by a direct-ion beam deposition method from pure acetylene and acetylenehydrogen gas mixtures. The lms were irradiated with a nanosecond Nd:YAG laser working at the rst harmonics (λ1 = 1064 nm), the fourth harmonics (λ4 = 266 nm) or with a Nd:YVO4 laser working at the third harmonic (λ3 = 355 nm). The lms were studied by the Raman scattering, micro-Fourier transform infrared and Fourier transform infrared spectroscopies, null-ellipsometry, optical and scanning electron microscope, and Vickers hardness method. Irradiation by the wavelength λ1 = 1064 nm leads to graphitization and formation of the silicon carbide, because of the silicon substrate decomposition. The samples were strongly modied after the irradiation by λ3 = 355 nm the thickness of the lms decreased, and silicon carbide was formed. It was observed that nano-structured materials (e.g. carbon nano-onions, nc-diamond) were formed after the irradiation by λ4 = 266 nm.