Ion beam synthesis of compound nanoparticles in SiO2

The ion beam synthesis of group IV (SiC) and II-VI (ZnS) compound nanoparticles in SiO2 layers is studied. These systems are potentially interesting for optoelectronic applications such as electroluminescent devices emitting in the visible and UV range. The combination of structural (transmission electron microscopy, electron and X-ray diffraction), optical (infrared and raman 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 part is dedicated to the synthesis of luminescent SiO2 layers co-implanted with 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 and SiC) leading to three intense, simultaneous and independent emission bands covering the whole visible range. A second part is dedicated to the synthesis of Mn doped ZnS nanocrystals. We have succeeded in synthesizing ZnS nanocrystals by sequential ion implantation in SiO2. The structural characterization of the annealed layers shows ZnS precipitates having a wurtzite-2H structure and with a quite narrow distribution of sizes. This population of 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 implantation 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 effective doping with Mn of the ZnS precipitates.