Pillars formed by laser ablation and modified by wet etching

Kurt W. Kolasinski; Margaret E. Dudley; Barada K. Nayak; Mool C. Gupta

doi:10.1117/12.724413

18 May 2007 Pillars formed by laser ablation and modified by wet etching

Kurt W. Kolasinski, Margaret E. Dudley, Barada K. Nayak, Mool C. Gupta

Proceedings Volume 6586, Damage to VUV, EUV, and X-ray Optics; 65860H (2007) https://doi.org/10.1117/12.724413
Event: International Congress on Optics and Optoelectronics, 2007, Prague, Czech Republic

Abstract

Studies on surface texturing by chemically enhanced laser ablation in a variety of materials, particularly silicon and germanium are reported. The materials are exposed either to femtosecond or nanosecond laser irradiation in a variety of vacuum or gaseous environments including air, He, sulfur hexafluoride (SF₆) or hydrogen chloride (HCl). The dynamics of pillar formation are elucidated and it is shown that the mechanisms are very different in these two pulse length regimes. Surface texturing responds to the combined effects of laser assisted chemical etching and laser ablation. Various processing steps either before or after laser irradiation allow us to modify the nature of the pillars that are formed. In this way we can make ordered arrays that extend over ≥1 cm² in just a few minutes of laser exposure. Post-laser processing wet etching can produce Si pillars that are over 50 &mgr;m long with tips that are only 10 nm across as well as macroporous silicon with crystallographically defined pores. A process we call solidification driven extrusion creates nanoscale spikes atop the pillars under certain circumstances - a process that is more prevalent for Ge than Si. Pillar-covered surfaces of Si and Ge are black; that is, they exhibit very low reflectivity. For Si this low reflectivity extends to wavelengths far below the band gap raising the possibility that we may be able to make other transparent materials highly absorptive by laser texturing.

Citation Download Citation

Kurt W. Kolasinski, Margaret E. Dudley, Barada K. Nayak, and Mool C. Gupta "Pillars formed by laser ablation and modified by wet etching", Proc. SPIE 6586, Damage to VUV, EUV, and X-ray Optics, 65860H (18 May 2007); https://doi.org/10.1117/12.724413

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