Volume 79, Number 2, July 2007
Article Number 26003
Number of page(s) 6
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 03 July 2007
EPL, 79 (2007) 26003
DOI: 10.1209/0295-5075/79/26003

Nanoscale observation of delayering in alkane films

M. 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 $T_{{\rm b}}$ 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 $T_{{\rm b}}$ and to a solid 3D phase on cooling below $T_{{\rm b}}$. 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