Structure And Characteristic Of Nanocrystalline β-Sic Films Prepared By Catalytic Chemical Vapor Deposition At Low Temperature

In my work, nanocrystalline β-SiC films were prepared by catalytic chemical vapor deposition (Cat-CVD) on single crystal Si (100) wafers, and quartz wafers. By adjusting parameters, the films with (111) preferential growth have been successfully obtained at a low temperature. The effects of various parameters on growth of the films were studied. It was observed that the size of particles in the films is decreased with the deposition pressure. By increasing the H2 dilution ratio, it is found that atomic hydrogen can selectively etch amorphous phase and stabilize crystalline phase. From the study on the distance from substrate to catalyzer, choosing a proper distance can ensure the gas fully decomposed, while a relatively low substrate temperature can cause the nanocrystalline particles to lose mobility and keep their sizes. The pre-carbonization process can enhance the nucleation density and make the growth of high quality nanocrystalline P -SiC films much easier. The application of the negative bias to the substrate accelerates ions in the plasma to the substrate surface. The accelerated ions increase active species on/above the substrate surface. Furthermore, ion bombardment against the growing surface is also conducive to enhance the nucleation density on Si substrate. Hence, it is considered that the high nucleation density integrated with low substrate temperatures causes the growth of nanocrystalline P -SiC films effectively.The Shimadzu UV-3101 spectrophotometer was employed to get the UV-Visible transmission and reflection spectra. Both of the absorption coefficient ( a ) and optical band gap (Eg) were calculated from the transmission and reflection spectra of the films. It was observed that Eg decreased with an increase in the deposition pressure.