Controlled CVD Growth of Highly < 111 >-Oriented 3C-SiC

Highly < 111 >-oriented 3C-SiC coatings with a distinct surface morphology consisting of hexagonally shaped pyramidal crystals were prepared by chemical vapor deposition (CVD) using silicon tetrachloride (SiCl4) and toluene (C7H8) at T <= 1250 degrees C and p(tot) = 10 kPa. In contrast, similar deposition conditions, with methane (CH4) as the carbon precursor, resulted in randomly oriented 3C-SiC coatings with a cauliflower-like surface of SiC crystallites. No excess carbon was detected in the highly < 111 >-oriented 3C-SiC samples despite the use of aromatic hydrocarbons. The difference in the preferred growth orientation of the 3C-SiC coatings deposited by using C7H8 and CH4 as the carbon precursors was explained via quantum chemical calculations of binding energies on various crystal planes. The adsorption energy of C6H6 on the SiC (111) plane was 6 times higher than that on the (110) plane. On the other hand, CH3 exhibited equally strong adsorption on both planes. This suggested that the highly < 111 >-oriented 3C-SiC growth with C7H8 as the carbon precursor, where both C6H6 and CH3 were considered the main active carbon-containing film forming species, was due to the highly preferred adsorption on the (111) plane, while the lower surface energy of the (110) plane controlled the growth orientation in the CH4 process, in which only CH3 contributed to the film deposition.