ИСТИНА

Femtosecond laser pulses with high emission intensity and low photon energy provide a possibility to achieve uniform nanostructuring and modification over the entire volume of siliceous films [1], and also lead to the anisotropy of their structural, electrical and optical properties. In addition, femtosecond laser processing can produce surface periodic structures [2]. Thus femtosecond laser radiation can be used to process amorphous hydrogenated silicon films (a-Si:H) for potential applications in photovoltaics. In this paper, a-Si:H films irradiated by femtosecond laser pulses (1250 nm, 100 fs) were investigated. Due to continuous movement of the laser beam in one direction and discrete movement in the perpendicular direction, so-called scan lines were formed. Scanning electron microscopy also revealed the presence of the one-dimensional grating-like structure with a period of about 0.36±0.03 μm on the treated surface. This surface periodic structure is perpendicular to polarization of the incident beam. This result is in agreement with the data of [3]. Electrical measurements have shown that the conductivity of a-Si:H film after irradiation with femtosecond laser pulses increased up to 3 orders of magnitude due to dehydrogenation and nanocrystallization of the film [4]. The conductivity along the scan lines and periodic structures is almost threefold greater than in the perpendicular direction. A possible explanation of this effect may be given by non-uniform crystallization of amorphous silicon, and the electric field anisotropic depolarization inside the surface periodic structure. 1. A. V. Emelyanov, M. V. Khenkin, A. G. Kazanskii, et al. Thin Solid Films 556, 410–413 (2014) 2. G.A. Martsinovsky, G.D. Shandybina, Yu.S. Dementeva et al. Semiconductors 43, 1339–1345 (2009) 3. R. Drevinskas, M. Beresna, M. Gecevičius et al. Appl. Phys. Letters 106, 171106 (2015) 4. A.V. Emelyanov, A.G. Kazanskii, P.K. Kashkarov et al. Semiconductors 46, 769–774 (2012)