Pit and mound formation on arc-evaporated carbon thin film using scanning tunneling microscopy

The etching of arc-evaporated carbon film with scanning tunneling microscopy (STM) was studied in comparison with that of highly oriented pyrolytic graphite (HOPG). The arc-evaporated carbon film was etched with STM only in air or in water vapor and at a sample bias voltage positive to the tip. These etching characteristics were similar to those for HOPG. After the carbon film was etched by a high bias voltage, the isolated carbon film was frequently exfoliated by STM scanning. On the other hand, a mound was also formed on the arc-evaporated carbon film below the tip when a high bias voltage (similar to 4 V) was applied to the film. The surface mound was formed at both polarities of the tip voltage and was not affected by atmospheric conditions. The mound area was characterized by Auger electron spectroscopy (AES). The Auger spectrum showed that the substrate material migrated to the carbon film.