STM Image Artifacts on Highly Ordered Pyrolitic Graphite That Could Be Mistaken for Carbon Nanotubes

Since the introduction of the national nanoscience initiative in 2000, many high schools across the country have started to introduce nanotechnology in their curriculum. The benchtop easy scan scanning tunneling microscope (STM) system is one of the most common instruments used in this nanotechnology classroom. This paper highlights some of the challenges involved in interpreting STM data when graphite is used as the substrate. Highly oriented pyrolytic graphite (HOPG) is a common substrate for STM studies of carbon nanotubes. It is an ideal surface for STM, because it is easily cleavable by adhesive tape, resulting in large, atomically flat planes that are relatively inert and electrically conducting. Despite these attractive attributes, the cleavage of HOPG surfaces also generates a variety of artifacts, some of which are elongated structures similar to the carbon nanotubes being investigated. Some even exhibit periodicities that mimic the atomic structures expected in the carbon nanotubes. In our investigation of carbon nanotubes deposited on a graphite substrate, we observed and catalogued many of these commonly known filament-like artifacts.