Femtosecond laser-induced damage morphologies of crystalline silicon by sub-threshold pulses

• Published in: Optics and lasers in engineering 2005-09, Vol.43 (9), p.977-986
• Main Authors: Tran, D.V., Zheng, H.Y., Lam, Y.C., Murukeshan, V.M., Chai, J.C., Hardt, D.E.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Femtosecond laser; Physical radiation effects, radiation damage; Physics; Silicon; Structure of solids and liquids; crystallography; Sub-threshold pulses; Surface damage morphologies; Ultraviolet, visible, and infrared radiation effects (including laser radiation)
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/j.optlaseng.2004.10.006

The effect of sub-threshold pulses of circularly polarized Ti:sapphire femtosecond laser system on crystalline (1 0 0) silicon wafer was investigated. Surface damage morphologies were studied by irradiating the test silicon surface with pulses (peak fluence of 0.25 J/cm 2) in succession. These pulses were below the single-pulse surface damage threshold. After the few initial pulses, the observed surface damage morphologies were found to be characterized by a minor phase change region and a major surface damage area at the center, corresponding to the well-known laser-induced periodic surface structure (LIPSS). Further increase in the number of pulses resulted in the formation of new surface morphologies with different features such as ablation, modification, and re-deposited materials. These features were reproducible and more distinguishable at higher number of pulses.