Amorphous to crystalline phase transition in pulsed laser deposited silicon carbide

Silicon carbide thin films are deposited on Si (100) substrates by ablating a SiC polycrystalline target in vacuum using a focused high power Kr F excimer laser. The effect of deposition temperature and laser intensity on the microstructure of the films is studied. Grazing Incidence X-ray Diffraction (GIXRD) is utilized to investigate the crystallographic phase and growth orientation of the deposited films. Their chemical bonding and structural ordering are deduced by Fourier Transform Infrared Spectroscopy (FTIR). Atomic Force Microscopy (AFM) was used to determine their surface roughness and morphology while paramagnetic defects were analyzed by the Electron Paramagnetic Resonance (EPR). It was found that the substrate temperature Td significantly affects the microstructure of the films. Indeed, (111) oriented 3C-SiC crystals are detected at Td greater than 800 degree C. But FTIR spectroscopy results show that the substrate temperature 625 degree C is a critical temperature at which structural changes occur in such a way that bonding is enhanced leading to a more ordered microstructure at higher temperatures. Si-C below 800 degree C, the films have a smooth surface morphology, whereas a sharp increase in roughness and diameter and particle height is detected above 800 degree C. These results agree with those obtained by GIXRD thus confirming that the onset of crystallinity in the layers takes place above 800 degree C. The EPR measurements indicate that the paramagnetic defects are typical of clustered carbon atoms whose arrangement are modified by varying Td. Temperature dependent EPR measurement confirm that a densification of the films take place around 625 degree C while a large scale crystallization occurs at 800 C. Increasing the laser energy E, from 200 to 400 mJ, has little effect on the microstructure of the SiC films but leads to the formation of larger grains. This work greatly contributes to understand the microstructural transition from the amorphous to the crystalline phase of pulsed laser deposited SiC films, which could have potential applications in fields encompassing optoelectronics, high power electronics and protective coatings (Author.)