Nanoscale observation of delayering in alkane filmsM. Bai1, K. Knorr1, M. J. Simpson1, S. Trogisch1, H. Taub1, S. N. Ehrlich2, H. Mo2, U. G. Volkmann3 and F. Y. Hansen4
1 Department of Physics and Astronomy and University of Missouri Research Reactor, University of Missouri-Columbia - Columbia, MO 65211, USA
2 National Synchrotron Light Source, Brookhaven National Laboratory - Upton, NY 11973
3 Facultad de Física, Pontificia Universidad Católica de Chile - Santiago 22, Chile
4 Department of Chemistry, Technical University of Denmark - IK 207 DTU, DK-2800 Lyngby, Denmark
received 11 January 2007; accepted in final form 4 June 2007; published July 2007
published online 3 July 2007
Tapping-mode Atomic Force Microscopy and synchrotron X-ray scattering measurements on dotriacontane (n-C32H66 or C32) films adsorbed on SiO2-coated Si(100) wafers reveal a narrow temperature range near the bulk C32 melting point in which a monolayer phase of C32 molecules oriented perpendicular to surface is stable. This monolayer phase undergoes a delayering transition to a three-dimensional (3D) fluid phase on heating to just above and to a solid 3D phase on cooling below . An equilibrium phase diagram provides a useful framework for interpreting the unusual spreading and receding of the monolayer observed in transitions to and from the respective 3D phases.
68.08.Bc - Wetting.
68.43.Hn - Structure of assemblies of adsorbates (two- and three-dimensional clustering).
87.64.Dz - Scanning tunneling and atomic force microscopy.
© Europhysics Letters Association 2007