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Discusses a photoluminescence (PL) study made on an oxygen-containing silicon fine structure fabricated by a gas evaporation technique. Transmission electron microscope micrographs of the samples; Size of the crystalline portion; Data on the PL spectra taken from samples formed under various preparation conditions.

The SiOx thin film with a thickness of about 1 mum was formed on a GaAs substrate by bar-coating with the organic solution of the SiOx nanoparticles (~40 nm). The as-formed SiOx thin film consists of the SiOx nanoparticles; thus the thin film is macroscopically discontinuous and is referred to as a nanoparticle thin film. Although there were no silicon (Si) nanocrystals in the as-formed SiOx nanoparticle thin film, Si nanocrystals were observed by Raman scattering measurement after the thin film was exposed to the laser beam. The growth of Si nanocrystals by laser irradiation is referred to as photosynthesis. The photosynthesis of Si nanocrystals is found to be a self-limiting process. After the average size reaches a certain value, further increase of irradiation time or laser power does not increase the average size. The photosynthesis is similar to the thermal synthesis of Si nanocrystals from SiOx but much faster and low-temperature growth of Si nanocrystals from SiO x. Furthermore, the laser irradiation makes nanoparticles larger by merging. This suggests a possibility of low-temperature formation of a Si-nanocrystal array embedded in a SiO2 thin film. Such a structure has many potential device applications [ABSTRACT FROM PUBLISHER]

Presents information on a study which examined photoluminescence with sub-band-gap photon energies in fine silicon (Si) particles prepared by the gas-evaporation technique. Preparation of the specimens; Performance of photoluminescence studies; Description of a typical spectrum measured for the Si fine particles.

Abstract: Both photo-oxidation and photosynthesis manifest a strong interaction between nanoparticles and photons due to the large surface area-to-volume ratio. The final sizes of the semiconductor nanocrystals are determined by the photon energy during these phenomena. The photosynthesis is demonstrated in a Si-rich oxide and is similar to thermal synthesis, which involves the decomposition of SiO x into Si and SiO2, that is well known and often employed to form Si or Ge nanocrystals embedded in SiO2 by annealing SiO x at high temperature. However, photosynthesis is much faster, and allows the low-temperature growth of Si nanocrystals and is found to be pronounced in the SiO nanopowder, which is made by thermal CVD using SiH4 and O2. The minimum laser power required for the photosynthesis in the SiO nanopowder is much lower than in the Si-rich oxide formed by the co-sputtering of Si and SiO2. This is attributed to the weak bond strength of Si–Si and Si–O in the SiO nanopowder. Photosynthesis, which can control the size and position of Si nanocrystals, is a novel nanofabrication technique making the best use of the strong interaction between photons and nanoparticles. [Copyright &y& Elsevier]

Abstract: Local vibration mode (LVM) infrared absorption from shallow thermal donors (STD) composed of nitrogen–oxygen complexes in nitrogen-doped CZ silicon crystals was examined. The samples whose STD concentration had been determined were measured. The sample dependence of the peaks at 810 and was similar to that of STD but the estimated concentration was slightly higher. New LVM peaks were found at 855, 973, 982, and so on. Their magnitude and sample dependence agreed well with those of STD. Annealing temperature dependence of other samples supported the results. Annealing time dependence of STD concentration at 650°C was examined. STD peaks at 250, 242 and those at 240, 234 and behaved differently, suggesting the presence of two kinds of STD origin. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]