VISIBLE PHOTOLUMINESCENCE AT ROOM-TEMPERATURE FROM MICROCRYSTALLINE SILICON PRECIPITATES IN SIO2 FORMED BY ION-IMPLANTATION

We have investigated the photoluminescence of microcrystalline silicon formed in SiO2 layers by ion beam synthesis. Si-28(+) ions over the d ose range 1 X 10(17) to 6 X 10(17) cm(-2) at energies of 150 keV and 2 00 keV were implanted into thermal oxide. Samples were annealed in a h alogen lamp furnace at temperatures of 900 degrees C, 1100 degrees C a nd 1300 degrees C for times between 15 and 120 min. The implanted laye rs were analysed by Rutherford Backscattering Spectroscopy (RES), Cros s-Sectional Transmission Electron Microscope (XTEM) and Photoluminesce nce (PL) (80 K to 300 K) using an Ar laser of 488 nm wavelength. Room temperature (300 K) visible photoluminescence has been observed from a ll the samples. XTEM confirms the existence of Si microcrystals (withi n the SiO2 layers), which typically have a diameter within the range o f 2-15 nm. The luminescence peak wavelength was about 600 nm or 800 nm , depending upon processing. Changes in the peak wavelength and intens ity from these samples and other samples in which the crystallites wer e reduced in size by thermal oxidation, show trends which are generall y consistent with quantum confinement, however, other mechanisms canno t be ruled out.