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 (VHF-PECVD) at 100 MHz in hydrogen diluted silane-methane gas mixtures. The substrate was kept at 250°C or 350°C 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 Back Scattering (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.
Laser induced crystallization of hydrogenated amorphous silicon-carbon alloys
DESALVO, AGOSTINO;IENCINELLA, DANIELE
2004
Abstract
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 (VHF-PECVD) at 100 MHz in hydrogen diluted silane-methane gas mixtures. The substrate was kept at 250°C or 350°C 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 Back Scattering (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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
