Photoluminescence of Si nanocrystals formed by the photosynthesis

Photosynthesis, which could control the size and position of Si nanocrystals being formed, as a novel nanofabrication technique making the best use of the strong interaction between photons and nanoparticles, is discussed in great detail. A nanocrystal growth is self-limited to the laser power and the laser-exposure time. The model is proposed to explain the self-limited growth and luminescence from the Si-rich oxide which was exposed to the laser. When the balance between the formation and loss of small amorphous Si clusters on the nanocrystal surface is maintained at a certain size, the nanocrystal growth will stop, and the final average size of the Si nanocrystals is achieved for each laser wavelength. The photoluminescence (PL) is observed when the Si nanocrystals are formed. The origin of the PL is associated with the small amorphous Si clusters, and its intensity increases with the increasing density of the Si clusters or photosynthesized Si nanocrystals. These small amorphous Si clusters remain particularly in the SiO nanopowder, which was made by thermal CVD using SiH4 and O2, even when the final average size is reached. The PL peak wavelength is well determined by the laser wavelength, which affects the structure of the small amorphous Si clusters and their light-emission energy. The photosynthesis is found to not only selectively form Si nanocrystals at low temperature, but also controls their size and even light-emission energy.