Structural Anisotropy of Amorphous Silicon Films Modified by Femtosecond Laser Pulses

• Published in: Optics and spectroscopy Vol. 124; no. 6; pp. 801 - 807
• Main Authors: Shuleiko, D. V., Kashaev, F. V., Potemkin, F. V., Zabotnov, S. V., Zoteev, A. V., Presnov, D. E., Parkhomenko, I. N., Romanov, I. A.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-06-2018; Springer Nature B.V
• Subjects: Amorphous silicon; ANISOTROPY; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Condensed-Matter Spectroscopy; CRYSTALS; ENERGY DENSITY; EXCITATION; Femtosecond pulses; Flux density; Gratings (spectra); HYDROGENATION; Laser processing; LASER RADIATION; Lasers; MODIFICATIONS; NANOSTRUCTURES; Optical Devices; Optics; Photonics; Physics; Physics and Astronomy; Polaritons; POLARIZATION; PULSES; RAMAN SPECTRA; SILICON; Silicon films; SURFACES
• ISSN: 0030-400X; 1562-6911
• DOI: 10.1134/S0030400X18060218

It is demonstrated that the surface-relief orientation in the form of one-dimensional gratings with a period of 1.20 ± 0.02 μm formed under processing of hydrogenated-silicon films by femtosecond laser pulses (1.25 μm) with an energy density of 0.15 J/cm
2
is determined by the direction of the polarization vector of the radiation and total laser exposure. Based on the results of the analysis of Raman spectra, the presence of a nanocrystalline phase of silicon with a volume fraction between 15 and 67% (depending on processing conditions) is detected. The observed processes of micro- and nanostructuring are caused by excitation of the surface plasmon–polaritons and nanocrystallization in the near-surface region in the field of high-power femtosecond laser pulses, respectively. In addition, formation of polymorph modifications of silicon Si-III and Si-XII under femtosecond laser processing with a number of pulses exceeding 500 is discovered. Anisotropy of the Raman signal for the above polymorph modifications is revealed.