GIANT SUPERSTRUCTURES FORMED ON GRAPHITE SURFACE-TREATED WITH NAOH SOLUTIONS STUDIED BY SCANNING-TUNNELING-MICROSCOPY

Giant superstructures with 1.71 and 9.1 nm lattice constants were obse rved by scanning tunneling microscopy (STM) on the surface of highly o riented pyrolytic graphite (HOPG) treated with NaOH solution. These st ructures were analyzed by the moire pattern hypothesis, For both the s tructures, the orientation angle mismatch of the giant lattices relati ve to the original atomic lattice of graphite was observed between the theoretical and experimental values. In addition, for the latter stru cture, the observed boundaries between the superstructural domain and the normal areas were straight, which is different from the theoretica lly predicted zigzag shape boundary. These discrepancies suggest the e xistence of some other mechanism responsible for the giant superstruct ures appearing in graphite intercalation compound surfaces. (C) 1998 E lsevier Science B.V. All rights reserved.