SILICON NANOPARTICLE FORMATION IN SI+-IMPLANTED THERMAL OXIDE-FILMS AND VISIBLE PHOTOLUMINESCENCE BEHAVIOR

We have investigated optical properties and microstructures of Si+-implanted thermal oxide films grown on crystalline Si wafer, as-implanted and after subsequent annealing. We found two types of visible luminescence bands similar to those of silica glasses: one peaked around 2.0 eV, observed in as-implanted specimens and annealed completely at about 600 degrees C, and the other peaked around 1.7 eV, observed only after heating specimens to about 1100 degrees C, the temperature at which Si segregates from SiOx. Though the shapes of these luminescence spectra are quite different from those having been observed in Si+-implanted silica glasses caused by interferences, the origins of these bands are the same as in silica glasses. Moreover, the direct evidence for the formation of nanometer-sized Si crystals in amorphous silicon dioxide matrix after annealing at 1100 degrees C is presented by high-resolution transmission electron microscopy.