Characterization of fluoroalkylsilane monolayer on polystyrene sphere arrays after plasma treatment

Polystyrene (PS) colloidal crystal films with well-ordered arrays of PS spheres treated with argon plasma and coated with fluoroalkylsilane (FAS) were characterized by means of spectroscopy ellipsometry, X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). The XPS analysis indicated that the FAS film on the plasma treated PS surface was a monolayer with an orderly packed CF3 group pointing outwards from the surface. The chemical composition of the PS surface changed immediately after a very short period of argon plasma treatment, while the subsequent coating of FAS on the plasma treated PS surface further modified the surface chemistry. The untreated PS surface exhibited poor interaction with FAS molecules. XPS and ToF-SIMS analyses showed the plasma treatment involved the oxidation of PS surface, where oxygen functional groups -O and O were generated, promoting FAS deposition on the plasma treated surface with strong secondary ion fragments originating from the FAS. The overall results indicated that plasma treatment was beneficial to the deposition of the FAS monolayer.