Photoluminescence And Growth Mechanism Of Au/SiO₂ Nanocomposite Films And SiO₂ Nanowires

One-dimensional nanomaterials have widely attracted attention due to their unique structural and electrical, optical, catalytic and mechanical properties. In recent years, as the important photoluminescence material, SiO₂ has been largely used in microelectronics and optical electronic industry. At present, one-dimensional amorphous SiO₂ nanoscale structures, like SiO₂ nanotubes and SiO₂ nanowires, have been prepared by various methods, but these one-dimensional nanomaterials remain less explored.This work includes two parts. First, we made use of the magnetron sputtering technology to sputter SiO₂ layers and Au layers on Si substrates and then to anneal at different temperature for 20 min (mode A) and at 1000℃for different annealing time (mode B). Second, we similarly utilized the magnetron sputtering technology to sputter only Au layers on Si substrates and to anneal with Si powder in N₂. Magnetron sputtering technique is one of practical methods of coating films. Regular surface covering film can be prepared by controlling the number of Au at the low temperature. Effect of annealing temperature and annealing time on the morphology and the photoluminescence of Au/SiO₂ nanocomposite films and growth mechanism of SiO₂ nanowires is analyzed preliminarily. The primary contents are as follows:1. Au/SiO₂ nanocomposite films were fabricated by two steps. First, SiO₂ and Au, were deposited on the Si substrates in turn by sputtering high-purity (99.999%) SiO₂ target and Au target in Ar. Second, as-deposited samples were annealed in the furnace in N₂ atmosphere.2. Surface morphology, crystallinity and the luminescent behavior of Au/SiO₂ nanocomposite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL). We analyzed the effect on the morphology and luminescence of Au/SiO₂ films at different temperature in a fixed annealing time and for different heating time at a fixed temperature. On increasing annealing temperature for 20 min, the size of Au crystallites in mode A first increases and then decreases. The intensity of the emission peak at 440 nm and 523 nm early increases and late decreases with increasing annealing time at 1000℃. The origin of the emission peak at around 440 nm was related to the size and quantity of Au particles and one of the emission peak at around 523 nm was relevant to the nanostructure of films.3. First of all, Au was deposited on the Si substrates by sputtering Au target in Ar and then as-deposited samples, Si power and Au/SiO₂ nanocomposite films samples prepared were annealed together in the furnace in N₂ atmosphere at 1100℃for 40 min. The length and diameter of SiO₂ nanewires prepared are almost uniform, which are about 30μm and 35 nm respectively. The growth of nanowires is consistent with the vapor-liquid-solid (VLS) mechanism, with Au particles being observed to remain at the tip of nanowires. Oriented amorphous SiO₂ nanowires were synthesized using Si powder as silicon source and using Au nanoparticles as the catalyst.4. Oriented amorphous SiO₂ nanowires were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and photoluminescence (PL). A sharp intensive green emission peak at around 519 nm was observed with the excitation wavelength at 325 nm due to neutral oxygen vacancies.