Thesis (M.Sc.) - Cairo University - National Institute of Laser Enhanced Sciences - Department of Laser Science and Interaction

Quantum dot nanocrystalline silicon (Si - nc) is recently attracting the interest of researchers in order to upgrade solar cells. New structural forms are still needed to improve its optoelectronic properties. Herewith, the fabrication of Si - nc from two types of silicon namely; p - type Si and pn - type Si wafers is reported. In this study Si nanocrystals were fabricated by liquid phase pulsed laser Ablation (LP - PLA) of silicon wafers immersed in double distilled water or ethyl alcohol. In this technique short duration laser pulses were focused onto the surface of the solid target embedded inside the liquid. Such focused laser provides high power beam that instantaneously ablate the solid into a plume of the target material under extreme conditions of temperature and pressure. The species in the plume, as atoms, ions, and clusters, traveling with high kinetic energy, under such typical non equilibrium conditions, are confined and vigorously interact within the high density domain providing new structures of the ablated solid in the form of nano - particles. One can clearly indicate that LP - PLA has become a successful material fabrication technique, allowing versatile design through choosing suitable solid targets and confining liquids. LP - PLA gained intensive attention for its ability to form more complex, better size distribution nanostructures and offered a way to study the dynamical processes among laser-solid-liquid interactions

Issued also as CD