High-resolution observations of an amorphous layer and subsurface damage formed by femtosecond laser irradiation of silicon

Using transmission electron microscopy (TEM), we observed the micro- and nanostructures of silicon after irradiation by ∼150fs duration pulses centered at 800nm wavelength. Specimens irradiated with a single pulse of 11J∕cm2 fluence and with five pulses, each with a fluence of 1.3J∕cm2, exhibited various structures which included amorphous phases. The amorphous phases were pure silicon, as was revealed by high-resolution TEM imaging, nanobeam …