Formation of Di-σ Bond in Benzene Chemisorption on Si(111)-7×7

Abstract

The adsorption of benzene on Si(111)-7×7 has been studied using high-resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). Both chemisorbed and physisorbed benzene were observed at an adsorption temperature of 110 K. Chemisorbed benzene desorbs molecularly at 350 and 364 K while physisorbed molecules desorb at 180 K. In the HREELS studies, two separate energy losses at 2920 and 3025 cm -1 were observed for chemisorbed benzene, attributable to the C-H stretching vibrations of sp 3 and sp 2 carbon atoms, respectively. In addition, the formation of Si-C bond is also evidenced at a vibrational frequency of 540 cm -1 . Our results clearly demonstrate that benzene is di-σ bonded to the adjacent adatom and rest atom on Si(111)-7×7, forming a 1,4-cyclohexadiene-like structure.

Substrate effect on supramolecular self-assembly: from semiconductors to metals

“…On the other hand, benzene has been shown to adsorb by establishing two Si-C bonds with an adatom and a rest atom instead of with a pair of adatoms, because of its reduced size. 3,43,44 As a consequence, we might speculate that TPA molecules adsorbed in the configurations of Fig. 3(a)-(d) might form two monodentate Si-O bonds with Si adatoms in the positions indicated by the corresponding ellipses in Fig.…”

Selective adsorption of coronene on Si(111)-(7×7)

“…More recently, aromatic hydrocarbons, although smaller than coronene, have been studied on this surface. Benzene is known to adsorb preferentially on the FH [17,18] forming di−σ bonds to an adatom−rest atom pair [19,20,21]. The sticking probability at the center adatoms is twice that at the corner adatoms, since the latter have one adjacent rest atom while the former have two.…”

Cycloaddition reaction of furan with Si(100)-2×1

“…A similar comparison was made for benzene binding on Si(111)-7ϫ7 and excellent agreement was achieved. 52,53 Therefore, on the basis of DFT calculations, it seems reasonable to assign the ␤1 desorption peak to the molecules adsorbed on the sites of A-B and/or A-C, and the ␤2 to the desorption from the A-D adsorption site.…”