Formation of Si nanocrystals in a-Si films using excimer laser

With the use of Raman scattering spectroscopy and electron microscopy techniques it was observed that nanosecond pulse excimer laser radiation impacts lead to formation into a-Si:H films on not-orienting glass substrates nanocrystals with preferred (110) orientation and sizes from 2 nm and bigger. The dependence of average size and concentration of nanocrystals on parameters of laser impacts (energy density and number of shots) was studied. Polarization anisotropy of the Raman scattering was observed in the system of mutual-oriented silicon nanocrystals. The analysis of polarization dependence of Raman scattering intensity makes possible to determine the part of the oriented nanocrystals. It is proposed, that preferred orientation is due to both elastic stress in the films and local deformations appearing around the nanocrystals. Features of "explosive" crystallization during excimer laser impact were observed. This effect can be result of significant mechanical stresses in a-Si:H films on glass substrates.