Comment on ‘Adsorption of ethylene on the Si(100)-(2 × 1) surface’ by C. Huang, W. Widdra and W. Henry Weinberg

Structure and Bonding of Ordered Organic Monolayers of 1,5-Cyclooctadiene on the Silicon(001) Surface

“…In Figure d, the structure of surface-bonded COD involves a four-membered Si 2 C 2 ring at the interface; this configuration implies that only the π bond of the silicon dimer is broken, with the σ bond intact. This “di-σ” bonding configuration is based on a similar configuration proposed in early studies of ethylene on Si(001) and leaves all Si and C atoms at the interface with a coordination number of four. , More recent experimental studies have suggested that both π and σ bonds of the SiSi dimers are broken during adsorption of ethylene on Si(001), leaving each Si atom with an unterminated dangling bond. − ,, Yet, previous ab initio calculations − have found the Si−Si σ bond to be intact, as we have depicted in Figure d. Our calculations, at the 6-31G level for COD on Si(001) and also at the Becke3LYP/6-31+G* level for ethylene on Si 9 clusters like those in Figure d, both predict that upon adsorption the Si−Si dimer bond lengthens to 2.42 Å, slightly longer than the 2.35 Å bond length found for unstrained Si−Si bonds by these same calculations but significantly shorter than the 3.84 Å separation that would be predicted if the Si atoms were in their bulk-truncated positions.…”

Adsorption of Phenyl Isothiocyanate on Si(001): A 1,2-Dipolar Surface Addition Reaction

“…This process would be expected to leave a NdCdS group bound through the N atom to a dimer. Silicon tetraisothiocyanate, Si(NCS) 4 , displays a very large NdCdS absorption feature, 49 so the absence of this absorption feature in Figure 1 is inconsistent with the presence of a Si-NdCdS surface species. Finally, the vibrational features at 2854 cm -1 (p-polarized) and 2849 cm -1 (s-polarized) observed in the monolayer PITC have been assigned previously as a combination band from a CdC stretch and the C-N stretch at 2850 cm -1 in liquid PITC.…”

Scanning Tunneling Microscopy of Organic Molecules and Monolayers on Silicon and Germanium (001) Surfaces

“…2(b). [10][11][12][13][14][15][16][17][18][19] Although many details of the mechanism of bonding remain uncertain, the reaction can thought of as arising through a mechanism in which the π bond of the Si = Si dimers and the π bond of the ethylene molecule are broken, forming two new Si-C π bonds. It should be noted that the molecules are not in fact standing vertically, but are tilted.…”