An infrared study of H8Si8O12 cluster adsorption on Si(100) surfaces

Abstract

Motivated by a controversy about the proper interpretation of x-ray photoelectron spectra of Si/SiO2 interfaces derived from the adsorption of H8Si8O12 spherosiloxane clusters on Si(100) surfaces, we have studied the adsorption geometry of the H8Si8O12 clusters on deuterium-passivated and clean Si(100) surfaces by using external reflection infrared spectroscopy. Access to frequencies below 1450 cm−1 was made possible through the use of specially prepared Si(100) samples which have a buried metallic CoSi2 layer that acts as an internal mirror. A comparison of the infrared spectrum of the clusters on a deuterium-passivated Si(100) surface at 130 K with an infrared spectrum of the clusters in a carbon tetrachloride solution reveals that the clusters are only weakly physisorbed on the D/Si(100) surface and also provides evidence for the purity of the cluster source. We also present infrared spectra of clusters directly chemisorbed on a clean Si(100) surface and show evidence that the clusters are adsorbed on the Si(100) via attachment by one vertex. A complete assignment of the observed vibrational features, for both physisorbed and chemisorbed clusters, has been made based upon comparisons with the results obtained in ab initio calculations using gradient-corrected density functional methods.

Chemisorption of H8Si8O12Clusters on Gold: A Novel Si−H Bond Activation

“…Valence band spectra were also obtained. The spectra show six key features between 7 and 17 eV that are identical with data previously obtained for H 8 Si 8 O 12 on Si(100) 7b 2 Soft X-ray Si 2p 3/2 core-level spectra of the interface derived from H 8 Si 8 O 12 chemisorbed to gold. …”

“…Monolayer assembly of discrete inorganic cage molecules has been reported during the past decade by a number of groups − metal halide and polyhedral borane clusters on gold, , and hydridosilsesquioxane clusters on silicon, germanium, and zinc selenide , This line of research is also being utilized to elucidate the surface role of cage complexes in important technological areas such as catalysis, corrosion protection, low-temperature dielectric formation, and lithography …”

Sorption mechanism and prediction of sorbents' behaviour in physicochemical systems

“…The evidence for this is the coincidence of a measured reflection IR spectrum and a calculated one (by the method of density functional). 165 Calculations have shown that an H 2 O molecule changes its configuration insignificantly upon its transition on regular adsorption centres localised at the faces (100) of NaCl crystals. But if a molecule of H 2 O gets near an anion vacancy in the nearsurface monolayer of the crystal, its electronic density changes so much that the molecule dissociates.…”

The reaction of H8Si8O12 with a chromium oxide surface: a model for stainless steel surface modification

“…The RAIRS spectrum of a thin chromium oxide film on chromium is shown (Fig. 3, spectrum 1) 30 and others on an Si(100) surface 31 . All of these features are consistent with the presence of HSiO 3 groups on the surface and the Si-O stretching frequency of 1175 cm À1 is indicative of intact spherosiloxane clusters and not amorphous SiO 2 .…”

“…31 The sum total of the core-level XPS, valenceband and RAIRS data can be simply interpreted as the clusters bound via one or more silicon vertices to surface oxygen atoms. In principle, the Si-H bending mode can provide information on the symmetry of the bound cluster, and therefore the coordination mode to the surface.…”