Controlled CVD growth of highly <111>-oriented 3C-SiC

Highly <111>-oriented 3C-SiC coatings with 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 ℃ and p = 10 kPa. In contrast, similar deposition conditions, using methane (CH4) as 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 using C7H8 and CH4 as carbon precursors is 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) surface. On the other hand, the CH3 exhibited equally strong adsorption on both planes. This suggests that the highly <111>-oriented 3C-SiC growth in the C7H8 process, where both C6H6 and CH3 are considered the main active carbon-containing film forming species, is due to the highly preferred adsorption on (111) planes, while the lower surface energy of the (110) plane controls the growth orientation in the CH4 process, in which only CH3 contributes to the film deposition.