Fabrication and characterization of fluorine-containing films using plasma polymerization of octafluorotoluene

Thin fluoropolymer films can be deposited by plasma enhanced chemical vapor deposition with precursor of octafluorotoluene (OFT). A transparent, yellow, hydrophobic and highly adhering film is formed on glass or polymethylmethacrylate (PMMA) substrates in a capacitively couple radio frequency (13.56 MHz) plasma system. Influence of the plasma parameters (r.f, power, deposition time, and pressure of monomer) on properties of the deposited films was investigated. Results indicate that the deposition rate of the octafluorotoluene plasma films increases with the increase of radio frequency (r.f.) power, reach maximum and then decreases. The increase of monomer pressure can enhance the deposition rate monotonically. However, the powdery film is formed when the monomer pressure is high than 140 mTorr. Hydrophobic surface with a water contact angle of 100 degrees was obtained by depositing OFT plasma film on the substrate. After water soaking treatment, the water contact angle of the plasma OFT films reduced to about 60 degrees. Xps and FTIR spectra indicate that the films contain significant amount of CEx (x = 1,2,3) groups and less amount of double bond groups (C=C, CF=CF). The stoichiometry of the films fluorine to carbon ratio (F/C) is 0.38 : 1, which is apparently lower than the starting OFT monomer (F/C 1.14 : 1). (C) 1999 Elsevier Science S.A. All rights reserved.