Femtosecond laser ablation of silicon-modification thresholds and morphology

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2002, Vol.74 (1), p.19-25
• Main Authors: BONSE, J, BAUDACH, S, KRÜGER, J, KAUTEK, W, LENZNER, M
• Format: Article
• Language: English
• Subjects: Ablation; Biological and medical applications; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Fluence; Fundamental areas of phenomenology (including applications); Impact phenomena (including electron spectra and sputtering); Industrial applications; Laser-beam impact phenomena; Lasers; Optics; Physical radiation effects, radiation damage; Physics; Pulse duration; Ripples; Silicon; Structure of solids and liquids; crystallography; Thresholds; Ultraviolet, visible, and infrared radiation effects (including laser radiation); Vaporization
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s003390100893

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/cm 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.