Tribology Letters

Surface diffusion and flow activation energies of perfluoropolyalkylether

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Surface diffusion of perfluoropolyalkylether (PFPE) Fomblin Z15 and Fomblin Zdol (hydroxyl terminated PFPE) on silicon wafers was investigated over the temperature range of 25 to 50°C using scanning microellipsometry. Zdol exhibits a much lower mobility and a distinctly different thickness profile as compared to Z15. The activation energy for surface diffusion of Zdol is higher than that of Z15, reflecting the stronger affinity of its hydroxyl end groups for the substrate. The viscosity flow activation energy Eη*is compared with that of surface diffusion Ed*yielding Ed*≈ Eη*for Z15, and Ed*≈ 1.5 Eη*for Z © 1995 J.C. Baltzer AG, Science Publishers.