Crystallinity in periodic nanostructure surface on Si substrates induced by near- and mid-infrared femtosecond laser irradiation

Reina Miyagawa; Daisuke Kamibayashi; Hirotaka Nakamura; Masaki Hashida; Heishun Zen; Toshihiro Somekawa; Takeshi Matsuoka; Hiroyuki Ogura; Daisuke Sagae; Yusuke Seto; Takahisa Shobu; Aki Tominaga; Osamu Eryu; Norimasa Ozaki

doi:10.1038/s41598-022-25365-1

Crystallinity in periodic nanostructure surface on Si substrates induced by near- and mid-infrared femtosecond laser irradiation

Sci Rep. 2022 Dec 5;12(1):20955. doi: 10.1038/s41598-022-25365-1.

Authors

Reina Miyagawa¹, Daisuke Kamibayashi², Hirotaka Nakamura^{2

3}, Masaki Hashida^{4

5}, Heishun Zen⁶, Toshihiro Somekawa⁷, Takeshi Matsuoka⁸, Hiroyuki Ogura², Daisuke Sagae², Yusuke Seto^{9

10}, Takahisa Shobu¹¹, Aki Tominaga¹¹, Osamu Eryu¹², Norimasa Ozaki^{2

3}

Affiliations

¹ Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya, 466-8555, Japan. miyagawa.reina@nitech.ac.jp.
² Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, 565-0871, Japan.
³ Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, 565-0871, Japan.
⁴ Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan.
⁵ Research Institute of Science and Technology, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa, 259-1292, Japan.
⁶ Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan.
⁷ Institute for Laser Technology, Nishi-ku, Osaka, 550-0004, Japan.
⁸ Institute for Open and Transdisciplinary Research Initiatives, Osaka University, Suita, Osaka, 565-0871, Japan.
⁹ Graduate School of Science, Kobe University, Kobe, Hyogo, 657-8501, Japan.
¹⁰ Department of Geosciences, Graduate School of Science, Osaka Metropolitan University, 3-3-138 Sugimoto Sumiyoshi, Osaka, 558-8585, Japan.
¹¹ Material Science Research Center, Japan Atomic Energy Agency, Sayo, Hyogo, 679-5148, Japan.
¹² Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya, 466-8555, Japan.

Abstract

Laser-induced periodic surface structure (LIPSS), which has a period smaller than the laser wavelength, is expected to become a potential technique for fine surface processing. We report the microscopic and macroscopic observations of the crystallinity of LIPSSs, where the characteristics such as defects generation and residual strain were analyzed, respectively. The LIPSSs were formed on a Si substrate using two different femtosecond pulses from Ti:Sapphire laser with near-infrared wavelength (0.8 μm) and free-electron laser (FEL) with mid-infrared wavelength (11.4 μm). The photon energies of the former and latter lasers used here are higher and lower than the Si bandgap energies, respectively. These LIPSSs exhibit different crystalline states, where LIPSS induced by Ti:Sapphire laser show residual strain while having a stable crystallinity; in contrast, FEL-LIPSS generates defects without residual strain. This multiple analysis (microscopic and macroscopic observations) provides such previously-unknown structural characteristics with high spatial resolution. To obtain LIPSS with suitable properties and characteristics based on each application it is paramount to identify the laser sources that can achieve such properties. Therefore, identifying the structural information of the LIPSS generated by each specific laser is of great importance.

Abstract

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