Atomic force microscopy measurements of topography in dotriacontane films adsorbed on SiO2 [abstract]
Abstract
Thin films of alkane molecules (chemical formula CnH2n+2) are of particular research interest in studies
of lubrication on the microscopic level. On one hand, alkane molecules serve as a simpler model for
more complex polymers used in coatings, adhesives and electronic devices. On the other hand, alkane
molecules are the primary constituents of commercial lubricants. Knowledge of the structure of a thin
film of alkane molecules could lead to a better understanding of lubrication on the microscopic level.
In our study, we have selected to study the alkane molecule dotriacontane (chemical formula C32H66).
We have chosen to use the technique of Atomic Force Microscopy (AFM) to study our dotriacontane
films. AFM is a technique that was developed in 1986 which is able to determine the topography of
films on a nano-scale, in particular our dotriacontane films. AFM utilizes a sharp tip that slides across
the surface of our film, detecting the various small changes in height. Using this technique, we can
determine the structure of dotriacontane films deposited from a heptane solution onto SiO2 coated
wafers. We find evidence that there are 1 to 2 layers of molecules with their long-axis parallel to the
plane of the surface, followed by a single layer of molecules with their long-axis perpendicular to the
plane of surface. In addition, we have evidence of islands consisting of more than one perpendicular
layer.