Laser CVD of cubic SiC nanocrystals

Nanocrystals of cubic silicon carbide (SiC) are formed using laser-assisted chemical vapor deposition. A CO2 laser beam is mechanically chopped to obtain pulsed infrared excitation. Silane (SiH4) and acetylene (C2H2) have been used as precursors. The formed SiC has the zinc-blende crystal phase (β-phase) with an average primary particle size of about 12 nm. As expected, higher chop frequencies yield smaller crystals. To establish electronic isolation between the particles, a native oxide shell of SiO2 can be formed by heating the particles in air. Subsequent etching with HF removes the oxide shell leading to further reduction of the particle size down to 4 nm.