THERMAL-DECOMPOSITION OF C2N2 ON SI(100)-2X1 AND SI(111)-7X7

The adsorption and thermal decomposition of C2N2 on Si(100)-2 x 1 have been investigated with TPD, XPS, UPS, and HREELS. For the C2N2 specie s, two desorption peaks at 160 and similar to 230 K were noted in the TPD spectrum, deriving from the C2N2 adsorbed in overlayers and the su bmonolayer, respectively.;The latter showed C-1s and N-1s XPS peaks at similar to 1.8 eV lower in binding energy than those of the multilaye r C2N2 The large energy shift in the XPS peaks is likely caused by the strong interaction between the C2N2 adsorbed side-on and the surface at lower coverages. Annealing the C2N2-doses Si(100) at similar to 600 K caused the breaking of the NC-CN bond, and the CN adspecies could b e identified on the surface. At 700-800 K, CN bond scission occurred, and thus a mixture of silicon carbide and silicon nitride was formed. Similar results were found for C2N2 on Si(111)-7 x 7; however, the rel ative signal intensities, e.g., C-1s and N-1s XPS and HREELS, are weak er than those of the C2N2 On Si(100). This difference may be attributa ble to the fact that there are fewer dangling bonds on Si(ll 1)-7 x 7 than on Si(100)-2 x 1.