Article

Applied Physics A

, Volume 74, Issue 1, pp 19-25

Femtosecond laser ablation of silicon–modification thresholds and morphology

  • J. BonseAffiliated withLaboratory for Thin Film Technology, Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin, Germany
  • , S. BaudachAffiliated withLaboratory for Thin Film Technology, Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin, Germany
  • , J. KrügerAffiliated withLaboratory for Thin Film Technology, Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin, Germany
  • , W. KautekAffiliated withLaboratory for Thin Film Technology, Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin, Germany
  • , M. LenznerAffiliated withLaboratory for Thin Film Technology, Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin, Germany

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Abstract

We investigated the initial modification and ablation of crystalline silicon with single and multiple Ti:sapphire laser pulses of 5 to 400 fs duration. In accordance with earlier established models, we found the phenomena amorphization, melting, re-crystallization, nucleated vaporization, and ablation to occur with increasing laser fluence down to the shortest pulse durations. We noticed new morphological features (bubbles) as well as familiar ones (ripples, columns). A nearly constant ablation threshold fluence on the order of 0.2 J/cm2 for all pulse durations and multiple-pulse irradiation was observed. For a duration of ≈100 fs, significant incubation can be observed, whereas for 5 fs pulses, the ablation threshold does not depend on the pulse number within the experimental error. For micromachining of silicon, a pulse duration of less than 500 fs is not advantageous.

PACS: 79.20D; 42.70.Q