Deposition of Stable and High Concentration of Carboxylic Acid Functional Groups onto Silicon Surface via a Tailored Remote Atmospheric Pressure Plasma Process
Deposition of Stable and High Concentration of Carboxylic Acid Functional Groups onto Silicon Surface via a Tailored Remote Atmospheric Pressure Plasma Process
Tuesday, May 2, 2017
Processes to introduce carboxylic acid functional groups onto surfaces have been widely applied on various applications, such as molecular grafting for biosensors, biocompatibility improvement, gas filter/adsorption in environmental engineering and the enhancement of interface adhesion between fillers (such as carbon or glass fibre) and matrix materials (such as epoxy resin) in composite materials.
To develop an environmental-friendly process to introduce a stable and high concentration of carboxylic acid functional groups, Acrylic Acid (AAc) was deposited on silicon wafers using argon Atmospheric Plasma Processing (APP) and vapour phase grafting in a bespoke Pyrex cylindrical chamber. The chamber stands vertically with an APP nozzle installed at the top, a sample platform downstream and an AAc vapour inlet on the chamber wall. In this way, both the effect of atmospheric gas on the process and AAc monomer fragmentation during APP can be limited. Silicon specimens were exposed to a combination of plasma gas and AAc vapour. Surface wettability was evaluated by measurement of water contact angles with chemical composition by X-ray Photoelectron Spectroscopy (XPS). The peak at the binding energy of 289 eV, which fits into COOH components in C1s spectrum of poly-AAc, was used to determine the contribution of the carboxylic acid groups depositing on the surface because it was absent in the C1s peak of untreated silicon wafers. A more stable and hydrophilic wettability and the binding energy peak at 289 eV from XPS show the presence of carboxylic acid groups on the surface of sample treated with AAc vapour with argon-APP. A higher intensity peak at 289 eV was detected, compared with the surfaces activated by an APP and subsequent AAc vapour grafting, suggesting a potential, rapid and novel APP process for carboxylic acid functional group deposition.
To develop an environmental-friendly process to introduce a stable and high concentration of carboxylic acid functional groups, Acrylic Acid (AAc) was deposited on silicon wafers using argon Atmospheric Plasma Processing (APP) and vapour phase grafting in a bespoke Pyrex cylindrical chamber. The chamber stands vertically with an APP nozzle installed at the top, a sample platform downstream and an AAc vapour inlet on the chamber wall. In this way, both the effect of atmospheric gas on the process and AAc monomer fragmentation during APP can be limited. Silicon specimens were exposed to a combination of plasma gas and AAc vapour. Surface wettability was evaluated by measurement of water contact angles with chemical composition by X-ray Photoelectron Spectroscopy (XPS). The peak at the binding energy of 289 eV, which fits into COOH components in C1s spectrum of poly-AAc, was used to determine the contribution of the carboxylic acid groups depositing on the surface because it was absent in the C1s peak of untreated silicon wafers. A more stable and hydrophilic wettability and the binding energy peak at 289 eV from XPS show the presence of carboxylic acid groups on the surface of sample treated with AAc vapour with argon-APP. A higher intensity peak at 289 eV was detected, compared with the surfaces activated by an APP and subsequent AAc vapour grafting, suggesting a potential, rapid and novel APP process for carboxylic acid functional group deposition.