THE OBSERVATION AND NEW MECHANISM OF AN ANOMALOUS SUPERPERIOD ON A HOPG SURFACE

We have observed an anomalous superperiod on a highly oriented pyrolyt ic graphite (HOPG) surface by scanning tunneling microscopy (STM) with period about 1.8 nm and amplitude about four times the ordinary atomi c amplitude. The orientation between this structure and the atomic lat tice is about 85.5 angle. After comparing several possible explanation s, we propose that the rotation between the surface layer and substrat e will give rise to a formation of CDW phase. Thus all the experimenta l results are well explained.