High-temperature atomic force microscopy of normal alkane C60H122 films on graphite

The morphology of ultrathin films of normal alkane C60H122 has been examined with atomic force microscopy at temperatures between 25 and 150 degreesC. 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 C60H122 molecule. A topmost layer was formed of nanocrystals up to 10 nm in height. The nanocrystals consist of multiple layers of C60H122 lamellae, which are oriented parallel to the substrate. Imaging of the alkane films at elevated temperatures has revealed that the nanocrystals melted around 95 degreesC, while the epitaxial layers have been observed at temperatures up to 140 degreesC. In some locations, a spontaneous reorientation of alkane lamellae has been noticed at temperatures in the 130-140 degreesC range.