High-Temperature Atomic Force Microscopy of Normal Alkane C60H122 Films on Graphite

The morphology of ultrathin films of normal alkane C 60 H 122 has been examined with atomic force microscopy at temperatures between 25 and 150 °C. The films were prepared by spin-casting of diluted alkane solutions on graphite. Epitaxial alkane layers, which are formed directly on the substrate surface, are characterized by lamellar morphology. A lamellar width of 7.5 nm corresponds to the length of the extended C 60 H 122 molecule. A topmost layer was formed of nanocrystals up to 10 nm in height. The nanocrystals consist of multiple layers of C 60 H 122 lamellae, which are oriented parallel to the substrate. Imaging of the alkane films at elevated temperatures has revealed that the nanocrystals melted around 95 °C, while the epitaxial layers have been observed at temperatures up to 140 °C. In some locations, a spontaneous reorientation of alkane lamellae has been noticed at temperatures in the 130−140 °C range.