Nanostructured films composed of silicon nanocrystals

Crystalline silicon nanoparticles were synthesized by laser pyrolysis of silane in a flow reactor. Afterwards the nanocrystals were extracted through a nozzle and shaped as a well-collimated molecular beam propagating under high vacuum. The nanocrystals produced in this way show strong photoluminescence (PL) that can be clearly ascribed to quantum confinement effects. In order to produce structured films being composed of these nanocrystals, we used the directivity of the beam and interposed a mask that defines the pattern. The crystals were then deposited on a substrate placed directly behind the mask. To check the resolution that can be obtained by these means, we have taken holey carbon films normally used for transmission electron microscopy. We have been able to create structures with lateral dimensions down to 30 nm. In another experiment, we have produced regular patterns of micrometer-sized spots being composed of Si nanocrystals. The photoluminescence behaviour of these structured films has been studied by laser scanning confocal microscopy.