Ion beam synthesis of compound nanoparticles in SiO2

The ion beam synthesis of group IV (SiC) and II-VI (ZnS) compound nanoparti cles in SiO2 layers is studied. These systems are potentially interesting f or optoelectronic applications such as electroluminescent devices emitting in the visible and UV range. The combination of structural (transmission el ectron microscopy, electron and X-ray diffraction), optical (infrared and r aman spectroscopies, optical absorption and photoluminescence) and physico- chemical (X-ray photoelectron spectroscopy, secondary ion mass spectroscopy ) techniques have been used to identify the phases formed and to correlate the optical behaviour of the layers with their microstructure. The first pa rt is dedicated to the synthesis of luminescent SiO2 layers co-implanted wi th Si and C. The presence of regions with different composition in terms of C content gives rise to the formation of 3 types of nanoparticles (Si, C a nd SiC) leading to three intense, simultaneous and independent emission ban ds covering the whole visible range. A second part is dedicated to the synt hesis of Mn doped ZnS nanocrystals. We have succeeded in synthesizing ZnS n anocrystals by sequential ion implantation in SiO2. The structural characte rization of the annealed layers shows ZnS precipitates having a wurtzite-2H structure and with a quite narrow distribution of sizes. This population o f nanocrystals is organized in two layers parallel to the free surface, as a consequence of a pure Ostwald ripening process or as a result of the impl antation damage distribution. The optical analysis of samples co-implanted with Mn shows the presence of a yellow-green and intense photoluminescence corresponding to an intra- Mn2+ transition, which demonstrates the effectiv e doping with Mn of the ZnS precipitates.