Adsorption and reactions of tetraethoxysilane (TEOS) on clean and water-dosed titanium dioxide (110)

The adsorption and reactions of tetraethoxysilane (TEOS) vapor on clean and water-predosed rutile TiO[sub 2]-(110) have been studied using temperature-programmed desorption (TPD), low-energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). The molecule sticks with a probabili...

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Bibliographic Details
Published in:Journal of the American Chemical Society 1993-12, Vol.115 (25), p.12096-12105
Main Authors: Gamble, L, Hugenschmidt, M. B, Campbell, C. T, Jurgens, Teresa A, Rogers, J. W
Format: Article
Language:English
Subjects:
400102 - Chemical & Spectral Procedures
400201 - Chemical & Physicochemical Properties
ADSORPTION
CHALCOGENIDES
Chemistry
DESORPTION
DISSOCIATION
Exact sciences and technology
FLUIDS
GASES
General and physical chemistry
HEAVY WATER
HYDRIDES
HYDROGEN COMPOUNDS
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
MATERIALS
MINERALS
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
REACTION INTERMEDIATES
RUTILE
SILANES
SILICON COMPOUNDS
SILOXANES
Solid-gas interface
SORPTION
SPECTROSCOPY
Surface physical chemistry
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
VAPORS
WATER
X-RAY SPECTROSCOPY
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Summary:The adsorption and reactions of tetraethoxysilane (TEOS) vapor on clean and water-predosed rutile TiO[sub 2]-(110) have been studied using temperature-programmed desorption (TPD), low-energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). The molecule sticks with a probability near unity at temperatures of 130-300 K, and at low coverage, TEOS dissociates upon heating. At higher coverages, some desorbs. On the water-and hydroxyl-free surface, the dissociation reaction occurs rapidly between 200 and 350 K, with the initial products being Si(OEt)[sub 15s] plus 2EtO[sub 3] (ET = C[sub 2]H[sub 5]). This is a new mechanism for silane coupling to oxide surfaces which requires neither hydroxyl groups nor surface defects. The EtO ligands, whether attached to Ti or Si atoms, decompose at approximately 650 K via [beta]-hydrogen elimination to yield ethylene gas and surface-bound hydrogen, which rapidly attaches to another EtO ligand, yielding ethanol gas. By 700 K, the net products evolved are equal amounts of ethylene and ethanol gas (two molecules of each per dissociated TEOS molecule), while SiO[sub 2] remains on the surface. 41 refs., 7 figs.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja00078a055