Laser induced crystallization of hydrogenated amorphous silicon-carbon alloys

Laser induced crystallization of hydrogenated amorphous silicon carbon alloy (a-Si1-xCx:H) films has been investigated by means of synchrotron x-ray diffraction. The a-Si1-xCx:H films were deposited on (100) silicon wafers by very high frequency plasma enhanced chemical vapor deposition at 100 MHz in hydrogen diluted silane-methane gas mixtures. The substrate was kept at 250 degreesC or 350 degreesC and the stoichiometry was changed from x=0.20 to 0.63. The structural characterization of the as-grown films has been carried out by Rutherford backscattering (hydrogen concentration) and infrared spectroscopy (film ordering). The films were irradiated by a KrF excimer laser (248 nm) with varying energy density and number of pulses. After irradiation, the formation of SiC crystallites has been revealed by synchrotron x-ray diffraction. Besides SiC nanocrystals, the formation of crystalline Si and graphite is observed for under- (x<0.50) and over-stoichiometric (x>0.50) samples, respectively. The essential role played by hydrogen concentration and hydrogen bonding configuration in determining the melting threshold and the consequent SiC grain formation is highlighted. (C) 2004 American Institute of Physics.