IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Biomaterials Tuesday Sessions
       Session BI+MM-TuM

Paper BI+MM-TuM5
Nano-Scale Effects on the Interfacial Fluidity of Organic Films

Tuesday, October 30, 2001, 9:40 am, Room 102

Session: Biomems & Microdevices
Presenter: R.C. Bell, Pacific Northwest National Laboratory
Authors: R.C. Bell, Pacific Northwest National Laboratory
M.J. Iedema, Pacific Northwest National Laboratory
K. Wu, Pacific Northwest National Laboratory
J.P. Cowin, Pacific Northwest National Laboratory
Correspondent: Click to Email
Interfaces cause fluids in nano-scale spaces to behave very differently than in bulk. We are able to spatially resolve this fluidity with 0.1 nm resolution and show how nanometer films of glassy 3-methylpentane (3MP) are much less viscous at the vacuum-in terface than at the 3MP-metal interface using ion mobility to probe the spatially varying flow properties. The amorphous 3MP films are constructed using molecular beam epitaxy on a Pt(111) substrate at low temperatures (<30 K). A 1 eV hydronium (D@sub 3@O @super +@) ion beam gently deposits ions on or into the films (the latter by depositing more 3MP on top of the ions). The ion motion is monitored electrostatically as the film is heated at a rate of 0.2 K/s above the bulk glass transition temperature of 3 MP (77 K). However, the ions begin to move at temperatures as low as 40 K near the vacuum interface, well below the bulk glass transition temperature. The viscosity near the vacuum-interface at 80 K is found to be 12 orders of magnitude lower than that ex pected of a bulk film. Furthermore, the fluidity perturbations were found to persist over 2.5 nm, which was determined by precisely placing the ions at increasing distances from the interfaces and monitoring the effect on the ion's mobility. Computer modeling is employed to further extract information about the nature of these films.