Formation process of Si nanoparticles in rare gas observed by a decomposition method

We have investigated the formation process of silicon nanoparticles after laser ablation of silicon targets in argon gas. The nanoparticles exhibit bright photoluminescence in the visible wavelength range and can be applied to opto-electronic devices. In order to observe silicon nanoparticles, we have developed a decomposition method. The nanoparticles were probed by detecting light emission resulting from decomposition using a second laser. This method enables us to observe nanoparticles that cannot be observed directly by the methods applied so far. We have observed that the nanoparticles grow in time periods of 1.0-1.8 ms following ablation in Ar gas at 5 Torr when Si targets are ablated at 5 J/cm² with a pulse width of 7 ns. The nanoparticles begin to grow above ablation spots slightly apart from the targets just after thermalization of the plume. We also found that the growth is delayed at higher fluxes of ablation laser light.