ELECTRONIC SUPERSTRUCTURES ON THE GRAPHITE SURFACE OBSERVED BY SCANNING-TUNNELING-MICROSCOPY - AN INTERFERENCE MODEL

Electron-density superstructures (SS) on highly oriented pyrolytic gra phite (HOPG) have long been observed near surface defects and surround ing metal particles by scanning tunneling microscopoy (STM). Xhie et a l. analyzed and catalogued ten such SS near Pt particles on HOPG [Phys . Rev. B 43 (1991) 8917]. Mizes and Foster suggested that the SS are t he result of interference between the normal electron waves and waves scattered by the metal particle [Science 244 (1989) 559]. This suggest ion was used by Shedd and Russell to introduce an interference model u sing simple electron wave functions and simulated two of the most comm only observed SS [Surf. Sci. 266 (1992) 259]. With this work we find t hat, by introducing a more general form for the electron wave function s and by considering multiple component interference, we can simulate many of the complex SS observed by STM, supporting the assertion that these SS are of an electronic nature and not a real surface reconstruc tion.