Growth of a SiC layer on Si(100) from adsorbed propene by laser melting

Carbon is incorporated into Si(100) to form a thin polycrystalline layer of SiC by laser melting the Si surface after adsorption of propene in ultrahi gh vacuum. The SiC layer of thickness up to 25 nm is polycrystalline. Cryst allites of size approximate to 100 nm are oriented with respect to the Si s ubstrate and exhibit a diffraction pattern in low energy electron diffracti on (LEED). The evolution of the surface is monitored in real time by record ing the Si transient reflectivity at 675 nm at each laser pulse, and after exposure to the laser by LEED, IR spectroscopy, and atomic force microscopy . The formation of the SiC layer is accompanied by very strong variations o f both the static and transient reflectivities, by the growth and narrowing of the IR peak assigned to beta SiC, and by the increase of the C incorpor ation rate. The SiC overlayer is very stable against photodesorption, while initially small amounts of C on Si are photodesorbed in a few laser pulses . Recording the transient reflectivity during processing allows one to evid ence that the laser absorption increases drastically as the SiC layer grows , resulting in (undesired) larger melting depth and duration that favor inc orporation of C in Si below the SiC layer. SiC layers of improved quality m ight be obtained by active control of the laser fluence by means of the ref lectivity transient. (C) 2001 American Institute of Physics.