Isoelectric points of plasma‐modified and aged silicon oxynitride surfaces measured using contact angle titrations

Acid-base properties of metal oxides and polymers can control adhesion properties between materials, electrical properties, the physical structure of the material and gas adsorption behavior. To determine the relationships between surface isoelectric point, chemical composition and aging effects, plasma-surface treatment of amorphous silicon oxynitride (SiOxNy) substrates was explored using Ar, H2O vapor, and NH3 inductively coupled rf plasmas. Overall, the Ar plasma treatment resulted in nonpermanent changes to the surface properties, whereas the H2O and NH3 plasmas introduced permanent chemical changes to the SiOxNy surfaces. In particular, the H2O plasma treatments resulted in formation of a more ordered SiO2 surface, whereas the NH3 plasma created a nitrogen-rich surface. The trends in isoelectric point and chemical changes upon aging for one month suggest that contact angle and composition are closely related, whereas the relationship between IEP and composition is not as directly correlated. Copyright © 2010 John Wiley & Sons, Ltd.