REACTION OF SI SURFACES WITH A C2H4 BEAM

The reactions of Si(100) and (111) surfaces with a C2H4 beam in ultrah igh vacuum were studied using high resolution X-ray photoelectron spec troscopy (WS) at temperatures of 600-900 degrees C. These reactions pr oduce silicon carbide (SiC) layers on the silicon surfaces, the growth rates of which increase with surface temperature up to about 675 degr ees C, but decrease at higher temperatures. The observed behavior is e xplained by the balance between the carbon supply rate from the C2H4 b eam and the silicon out-diffusion rate from the substrate to the carbi de surface. The carbon supply rate is limited by the surface residence time of chemisorbed C2H4 and the beam flux. At the temperature of max imal growth the composition ratio of carbon to silicon in the carbide layer is close to unity, but decreases with increasing temperature. Be low the optimal temperature the FWHM of the C Is XPS peak is broader t han that of the stoichiometric compound SiC, implying that the chemica l bonding in the carbide layer is distributed. The SiC bulk plasmon-lo ss peaks accompanying the Si 2s and C Is XPS peaks appear in carbide f ilms thicker than about 13 Angstrom.