ИСТИНА

In this work amorphous hydrogenated silicon (a-Si:H) films were irradiated by femtosecond laser pulses (λ = 1250 nm, τ = 125 fs, f = 10 Hz) in raster mode. Laser-induced periodic surface structures (LIPSS) with period close to laser wavelength were revealed by scanning electron microscopy on the irradiated a-Si:H surfaces. Formation of such structures is caused by nonequilibrium carriers photoexcitation and subsequent surface plasmon-polaritons generation. Dark conductivity of modified films increased by 3 orders of magnitude according to electrical measurements, due to formation of nanocrystalline silicon phase after femtosecond laser treatment. According to Raman spectra, nanocrystalline phase volume fraction was from 17 to 45% depending on modification conditions. Also, dark conductivity and charge carriers mobility demonstrated artificial anisotropy in the irradiated a-Si:H films. Observed anisotropy can be explained both by LIPSS depolarizing effect and non-uniform film crystallization within raster lines and LIPSS.