Epitaxial cubic SIC thin films have been deposited on Si(111) by supersonic molecular jet epitaxy of the single source precursors of methylsilane (MS), CH3SiH3, and dimethylethylsilane (DMES), (CH3)(2)SiH(CH2CH3), at temperatures in the range 780-950 degrees C. Single crystalline, crack-free epitaxial cubic SiC thin films were successfully grown on carbonized Si(111) substrates at temperatures as low as 830 degrees C using MS and DMES. Highly oriented cubic SiC thin films in the (111) direction were obtained on uncarbonized Si(111) substrates at 780 degrees C using MS and at 950 degrees C from DMES. However, the growth temperature of DMES was lowered to 830 degrees C on Si(111) when the substrates were initially carbonized with a supersonic jet of acetylene. Below 780 degrees C, moreover, only polycrystalline cubic SiC thin films were grown on either carbonized or uncarbonized Si(111) surfaces with MS. The advantage of supersonic molecular jets of the single source precursors employed in this study is evident in that the surface carbonization process may not be necessary, and the deposition procedure is quite simple and safe to handle. Real-time, in situ optical reflectivity was used to monitor the film growth. The as-grown films were characterized in situ by Auger electron spectroscopy (AES) and ex situ by ellipsometry, SEM, FTIR, UV/Visible spectroscopy, and XRD (especially omega and phiscan measurements).