THE MORPHOLOGY OF LAMELLAR C-70 SINGLE-CRYSTALS AS STUDIED BY ATOMIC-FORCE MICROSCOPY

C-70 single crystals were grown using the vapor phase transport techni que. Lamellar growth was evident on the surfaces of some crystals. The bulk structure of these crystals was confirmed to be hexagonal closed -packed (hcp) by X-ray diffraction. The surface morphology of the lame llar crystals was investigated using atomic force microscopy (AFM). In the lamellar growth areas, micrometer sized (0001), (<10(1)over bar 0 >), and (<01(1)over bar 0>) faces were observed in low resolution AFM images. For the first time, AFM images have been obtained for all of t hese faces. The AFM images revealed that lamellar growth originates in regions in which three types of faces can co-exist near the edges of the crystal. A monolayer-spreading growth mechanism was inferred from the layered structure images. High resolution images were obtained on the (0001) and the (<10(1)over bar 0>) faces. It was observed that the molecules on the (0001) face were arranged in a slightly distorted he xagonal arrangement, with an average nearest-neighbor distance alpha = 10.5 +/- 0.3 Angstrom. On the (<10(1)over bar 0>) face, the molecules were arranged in a distorted rectangular unit (with alpha = 75 degree s +/- 3 degrees), with alpha = 10.5 +/- 0.3 Angstrom and c = 19.0 +/- 0.3 Angstrom. On both faces, a long-axis disorder of the surface C-70 molecules was suggested. The surface molecular arrangements were able to be resolved, exhibiting a distorted hcp structure.