Silicon Nanostructured Films Formed by Pulsed-Laser Deposition in Inert Gas and Reactive Gas

We reported Si nanostructured films formed by pulsed-laser deposition (PLD) in both inert Ar gas and reactive O2 gas. The as-deposited nanostructured films with visible photoluminescence (PL) show a transition from a film structure to a porous cauliflowerlike structure, as the ambient gas pressure increases from 1 mTorr to 1 Torr. The film consists of small crystals with size from 1 to 20 nm. The oxygen composition of SiOx increases with increasing O2 gas pressure, while Si 2p peak of the Si dioxide also becomes dominate. At 100 mTorr O2 gas, almost complete SiO2 structure is formed. The PL at 1.8–2.1 eV is attributed to the quantum confinement effect (QCE) in Si nanocrystal core, while the PL band at 2.55 eV can be explained by the light emission from the localized surface states at SiOx/Si interface. Laser annealing was applied to the as-deposited nanostructured films. The PL intensities are increased by about two to three times of magnitude after annealing. High laser fluence causes damages in the films and optimal laser fluence exists before film damages or laser ablation occur.