Cyclopentene (c-C 5H 8) adsorption on Si(0 0 1)-2 × 1 and on dimer vacancies on the surface: A theoretical study of the electronic structure and chemical bonding

Abstract

In the present work we analyzed the geometry and the chemical interactions of c-C 5H 8 after adsorption on a semiconductor surface: Si(0 0 1), by density functional theory calculations (DFT). Using a slab model, we studied the changes in the atomic and orbital interactions corresponding to the system. We examined overlap population values for specifics bonds during the adsorption. We considered two cases, the cyclopentene adsorption on dimers on the surface and on dimer vacancies on Si(0 0 1). We found an average C Si distance of 1.96 Å on dimer Si Si; and an average H Si, C Si, and C Si distances of 1.59 Å, 1.83 Å, and 1.57 Å respectively on dimer vacancies. We also studied the density of states (DOS) and the crystal orbital overlap populations (OPDOS) corresponding to C C, C Si, C H, and Si Si bonds. The main contribution to the adsorption are the C C double bond in both cases and the H’s belonging to this double bonds in the case of adsorption on dimer vacancies (DV). The orbital contribution includes participation of the 2p z orbitals corresponding to C atoms and 3p z orbitals corresponding to Si in the case of adsorption on Si(0 0 1)-2 × 1 surface, and 2p x , 2p y , and 2p z orbitals corresponding to C atoms, and the 3p x , 3p y , and 3p z orbitals corresponding to Si for cyclopentene adsorption on DV. The adsorption of cyclopentane on Si(0 0 1)-2 × 1 produce several vibrational frequencies similar to that of c-C 5H 10, a molecule with sp 3 hybridization. After C 5H 8 adsorption no frequencies coming from a C C bond are computed which also support the idea of re-hybridization. On DV the Si C frequency increase 35 cm −1, indicating a stronger bond with the surface.