Nanoscale observation of delayering in alkane films

• Published in: Europhysics letters Vol. 79; no. 2; pp. 26003 - p1-26003-p6
• Main Authors: Bai, M, Knorr, K, Simpson, M. J, Trogisch, S, Taub, H, Ehrlich, S. N, Mo, H, Volkmann, U. G, Hansen, F. Y
• Format: Journal Article
• Language: English
• Published: United States IOP Publishing 01-07-2007; EDP Sciences
• Subjects: 68.08.Bc; 68.43.Hn; 87.64.Dz; ALKANES; ATOMIC FORCE MICROSCOPY; COOLING; EQUILIBRIUM; FLUIDS; HEATING; MELTING POINTS; MOLECULES; national synchrotron light source; PARTICLE ACCELERATORS; PHASE DIAGRAMS; SCATTERING; SOLIDS; SYNCHROTRON RADIATION; TEMPERATURE RANGE; X-RAY DIFFRACTION
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/0295-5075/79/26003

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.