Covalent surface modification of silicon oxides

Date created: 
Microwave, surface modification, silicon oxides, self-assembled monolayer, hydrophobicity, oleophobicity, alkylsilanes, alcohols

Microwave radiation was utilized as a tool to modify surface properties of silicon oxides. Covalent surface modification of silicon oxides has been widely pursued in the areas of material science, electronics, microfluidics, biology, and separation science. Chemical surface modifications are often achieved through the formation of organic monolayers, often referred to as self-assembled monolayers (SAMs). While these organic monolayers have been proposed as an effective surface modification strategy, the defects in these organic monolayers compromise the effectiveness on their ability to alter surface properties. For example, in the case of passivation of microscale electronic devices, the surfaces that are not covered by the organic monolayers are susceptible to environmental stress or corrosion, which can cause detrimental failures of the devices. Traditional methods of formation of monolayers often cause many defects including formation of multilayers or micelles, physically adsorbed organic film, and/or voids. In this thesis, microwave radiation is utilized as a tool to accelerate the formation of uniform monolayers. In particular, the formation of silane based monolayers and alcohol based monolayers on silicon oxide surfaces have been extensively studied. Microwave heating, unlike the traditional heating methods, delivers the thermal energy to the substrate surfaces. It can effectively accelerate the formation of both silane and alcohol based monolayers. Alcohol based reagents, in particular, is proposed as an alternative building blocks for their widespread availability and minimal reactivity with moisture. Tuning of surface chemistry of silicon oxides have been achieved with alcohol based regents with different functional groups. Furthermore, the formation of mixed monolayers has been proposed as means of controlling oleophobicity of the silicon oxide surfaces. Finally, the film thickness of the alcohol based monolayers has been characterized with angle-resolved X-ray photoelectron spectroscopy (ARXPS). The film thickness can be precisely tuned by choosing the alcohol based reactants with particular lengths of alkyl chains. A variety of surface chemistry can be designed towards many practical applications requiring surface functionalized silicon oxides using the research presented herein.

Document type: 
This thesis may be printed or downloaded for non-commercial research and scholarly purposes. Copyright remains with the author.
Senior supervisor: 
Byron D. Gates
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.