Preparation of chemical gradient surfaces by hyperthermal polyatomic ion deposition: A new method for combinatorial materials science

C3F5+ ion deposition at 50 eV is used to produce chemical gradient surfaces on poly(methyl methacrylate) (PMMA) by systematic variation of the fluence across the surface. The gradient is characterized by recording small spot X-ray photoelectron spectra and air/water contact angles along the sample length. The fluorine content grows with ion fluence toward the modified end of the sample while the oxygen content decreases simultaneously. These two effects are attributed to the formation of a fluorocarbon film on top of the PMMA surface, which increases in coverage with C3F5+ ion fluence. The air/water contact angle increases in parallel with the fluorine content along the surface gradient. These results clearly indicate that a chemical and wettability gradient is produced on PMMA by mass-selected hyperthermal ion deposition. C3F5+ ion deposition can also be used to produce chemical gradient surfaces on polystyrene, aluminum, and silicon substrates. It is shown that hyperthermal polyatomic ion deposition is a general method for a wide range of surface chemical gradients on various substrates including polymers, metals, semiconductors, and ceramics.