Ultrahigh vacuum scanning probe microscopy studies of carbon onions

Carbon onions were prepared by DC arc charge method. The behavior and electronic properties of carbon onions on highly oriented pyrolytic graphite (HOPG) substrate were studied by ultrahigh vacuum atomic force microscopy and scanning tunneling microscopy (UHV AFM/STM). UHV AFM/STM images showed that these ellipsoidal carbon onions tended to aggregate into clusters on the surface of HOPG. The scanning tunneling spectroscopy indicated that the electrical properties of carbon onions were between graphite and single-shell fullerenes.