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Femtosecond Pulsed Laser-induced Ablation Region Development on the Surface of Silicon
D-Q. Yuan, M. Zhou, N-F. Ren and J-T. Xu

The effect of sub-threshold pulses from a Ti:sapphire femtosecond laser system on silicon (100) wafer was investigated. Surface damage morphologies were studied by irradiating the test silicon surface with pulses (fluence of 1.13 J/cm2) in succession. We investigated the effects of pulse number on the evolvement of ablation area when the pulse fluence was kept consistent. For 15 pulses there were only two regions in the irradiation area. With increasing the pulse number to 35, the irradiation area could be divided into four regions. The pulse number at the range of 50 to 400, there were five regions. With further increasing the pulse number above the 800, the irradiation area could be divided into six regions; also, the pattern of columnar structure was formed in the centre region of irradiation area. The phenomenon of evolvement of irradiation area when increasing the pulse number was due to the accumulation of multiply pulse radiation.

Keywords: Femtosecond laser, silicon, ablation region, sub-threshold, morphology, ripples, columnar

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