Abstract : In Near-eld Scanning Optical Microscopy (NSOM), a sub-wavelength source of light is driven in the vicinity of the sample studied, at small distances compared to lambda. Raster scanning the probe in front of the sample allows one to build an image with a resolution limited by the size of the source of light, not by diffraction. A single nanoparticle (size smaller than 10 nm) as source of light would allow one to reach genuinly nanometric resolutions.
A dual confocal/NSOM microscope has been developped, in order to study and use such nanoparticles. Thanks to that microscope, images using the fluorescence of a single CdSe/ZnTe nanocrystal (~ 4 nm), attached to the apex of a standard NSOM tip, as source of light, have been acquired. The fluorescence blinking and photobleaching of those nanocrystals prevented us from building a complete image and therefore no discussion about the resolution reached is possible. We investigated other nanoparticles exhibiting no luminescence blinking or bleaching. The first candidate is YAG :Ce3+ agregates produced by LECBD, whose size is under 5 nm. The first optical caracterizations of those particles are presented.
The second candidates are diamond nanoparticles doped by NV-centres. We show that our experimental set-up allows to select the luminescent particles, quantify their size and nd the ones that are doped with a single centre. Moreover it is possible to in-situ determine the charge of the center. Thus we demonstrate that our NSOM easily detects a single NV centre in a 25 nm diamond nanoparticle. This opens the possibility to use a particle of size as small as possible as source of light.