Investigation of a Vapor-Deposited Thin Silica Film: Morphological and Spectral Characterization

Abstract

Surface modification reactions by organosilicon compounds have demonstrated great success in a wide variety of applications. However, they are of limited usefulness in that they only proceed appreciably on surfaces that have an abundance of reactive hydroxyl groups, thus preventing their application to some materials of technological relevance, such as plastics and polymers. A process capable of depositing a surface rich in reactive hydroxyl groups onto a wide variety of substrates could potentially enable the extension of organosilane surface modification reactions to new materials, but conventional processes for depositing oxide layers require temperatures that are too high for most polymers and plastics. It has been shown that silica layers can be deposited from the vapor-phase hydrolysis of tetrachlorosilane at room temperature, but little if any work has been done to characterize the resulting films. In this work, ellipsometry, atomic force microscopy, and Fourier transform infrared spectroscopy are employed to study the characteristics of films formed from this process. Interestingly, very different film morphologies can be obtained by changing key processing parameters. Furthermore, isotopic exchange experiments and dehydration studies show that the surfaces of the silica films obtained by this method are composed entirely of hydrogen-bonded silanol groups and do not exhibit any freely vibrating surface silanol groups, a result that is in contrast with conventionally prepared silica materials. Still, this layer has been shown to behave very similarly to conventional silica materials with respect to surface reactions. Finally, infrared spectral data and contact angle data demonstrate that this method can be employed to deposit silica layers onto poly(methyl methacrylate) and polystyrene surfaces.

Effects of Gas or Vapor Adsorption on Adhesion, Friction, and Wear of Solid Interfaces

“…When the silica surface was treated with poly(ethylene oxide), the isotherm thickness and the structure of the adsorbed water layers was altered significantly. 33 Similar deviations were observed for water adsorption in porous silica films. 33 Octadecylsilane SAMs are often produced on silica surfaces to obtain water repellency because this SAM gives a water contact angle higher than 90°.…”

“…33 Similar deviations were observed for water adsorption in porous silica films. 33 Octadecylsilane SAMs are often produced on silica surfaces to obtain water repellency because this SAM gives a water contact angle higher than 90°. Although well-defined covalently attached silane SAMs can be reproducibly prepared, there is always disorder in the alkyl chain packing.…”

“…In other words, the completely dehydroxylated silica surface is hydrophobic. When the silica surface was treated with poly(ethylene oxide), the isotherm thickness and the structure of the adsorbed water layers was altered significantly . Similar deviations were observed for water adsorption in porous silica films …”

High efficiency amine functionalization of cycloolefin polymer surfaces for biodiagnostics

“…[17][18][19][20] However, most published investigations have concerned the simple vapourphase reaction of aminosilanes with a hydroxylated surface, usually glass or silicon at high temperatures that are not suitable for COP chips. 21,22 In contrast to the multi-step complexity of the methods described above, we have found that a fast and simple route to versatile amine-functionalized surfaces on COP plastics is to combine the oxygen plasma activation method with plasma enhanced chemical vapour deposition (PECVD) from an aminated precursor. PECVD, a single step high throughput process, is a versatile surface engineering technique which has proven to be an excellent tool for surface modification and large scale production that does not leave behind liquid waste.…”

Enabling Organosilicon Chemistries on Inert Polymer Surfaces with a Vapor-Deposited Silica Layer

“…We have previously investigated the deposition process and characterized the surface chemistry of thin silica films formed by the room-temperature, vapor-phase hydrolysis of tetrachlorosilane . We have also demonstrated that these films support organosilane surface modification chemistries using conventional solvent techniques, resulting in monolayers with thermal and aqueous immersion stability properties indistinguishable from those deposited on native silicon oxide surfaces .…”