Core-level spectroscopy of hydrocarbons adsorbed on Si(100)-(2X1): A systematic comparison - art. no. 045308

Adsorbate and substrate core-level binding energies for adsorption layers o f six unsaturated hydrocarbons (C2H2. C2H4, C3H4, C4H6, C6D6 (C6H6), and 1, 2-C2H2Cl2) on the Si(100)-(2x1) surface have been determined by high-resolu tion x-ray photoemission spectroscopy; results for the clean and the (2x1)- H covered surface have been obtained for comparison. Remarkable differences in the Si 2p and C 1s surface core-level shifts for the various adsorbates are found. which range from 327 to -169 meV and from 1220 to -260 meV, res pectively. Both initial- and final-state effects are necessary to explain t he strong but unsystematic variations of the observed shifts. Additionally, from a comparison of the C Is intensities the absolute saturation coverage s are determined to be 0.87, 0.84, 1.15, 0.79, 0.36. and 0.44 molecules per unit cell of the clean surface for C2H2, C2H4, C3H4, C4H6, C6D6, and 1,2-C 2H2Cl2, respectively.