Laser CVD of silicon nanoclusters and in-situ process characterization

Raman scattering in combination with laser-induced fluorescence (LIF) has b een used to identify intermediates during the nucleation and growth of nano sized silicon clusters created by CO2 laser excitation of silane. Upon swit ching on the CO2 laser, the silane Raman peak height decreases due to a dec rease in species number density and LIF peaks emerge due to presence of SiH 2 radicals. Also a Raman signal of Si2H6 is observed. The dissociation temp erature is determined inside the reaction zone with rotational Raman of H-2 and equals 605 K which is far below the thermal decomposition temperature of silane. Amorphous silicon nanoclusters are formed and show remarkable op tical effects which can be explained with quantum confinement of excitons. The size of these clusters is between 0.8 and 3 nm.