Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) study of SF 6 and SF 6 –CF 4 plasma‐treated low‐density polyethylene films

• Published in: Surface and interface analysis 1995-07, Vol.23 (7-8), p.467-476
• Main Authors: Léonard, D., Bertrand, P., Khairallah‐Abdelnour, Y., Arefi‐Khonsari, F., Amouroux, J.
• Format: Article
• Language: English
• ISSN: 0142-2421; 1096-9918
• DOI: 10.1002/sia.740230706

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) is used to monitor in a semi‐quantitative way the chemical modifications produced at low‐density polyethylene (LDPE) film surfaces by SF 6 and SF 6 –CF 4 plasma treatments. The influence of the plasma treatment time (SF 6 plasma) and the gas composition (SF 6 –CF 4 plasma) have been investigated. The ToF‐SIMS results are compared with plasma diagnostics (mass spectrometry and optical emission spectroscopy) and with some earlier XPS characterization. The ToF‐SIMS study of SF 6 plasma‐treated LDPE films as a function of the treatment time shows two different structural developments. Beside the expected formation of C x F y structures due to the grafting of F atoms, ToF‐SIMS detects the presence of SF x species at the surface. Their high sensitivity to ablation, due to the plasma ions, was related to two possible interactions of plasma species with the LDPE surface: an adsorption of SF x +/− ions or a dissociative chemisorption of SF x neutral species. In the latter case, the low binding energy of the SC bond can explain the high sensitivity to ablation. In the case of SF 6 –CF 4 plasma treatment, the incorporation of fluorine, as seen by ToF‐SIMS, is a function of the gas composition. Two maxima are observed when the second gas (either SF 6 or CF 4 ) is introduced at low concentration (∼10%). These maxima are confirmed by XPS and actinometric results and are explained with respect to the reciprocal influence of both gases in the plasma discharge.