Maleic anhydride adsorption on silicon (001)

The adsorption of maleic anhydride on the Si(001) surface has been investigated using the first-principles pseudopotential formalism. Our total-energy calculations suggest that maleic anhydride (C2H2-C2O3) adsorbs preferentially through a [2+2] cycloaddition of the C=C bond ([2+2]) with an adsorption energy of around 42 kcal/mol. Besides the [2+2] configuration we have also considered other possible coverages and adsorption models, including the adsorption on inter-row and intrarow dimer sites. Based on the analysis of the relative stability of different adsorption models, we propose the formation of mixed domains, containing the [2+2] unit and an interdimer unit. The comparison of our calculated electronic band structure, vibrational modes, and scanning tunneling microscopy images for the [2+2] and the favored interdimer adsorbed structures corroborate our proposed mixed domain model.