The electronic properties of suspended single wall carbon nanotubes

Abstract We have performed STM measurements on suspended single wall carbon nanotubes at room temperature in order to probe their intrinsic electronic properties. Comparing with supported nanotubes, we find that substrate–nanotube interactions influence the electronic properties. On supported semiconducting nanotubes bands are shifted toward higher energies while they are more symmetric around the zero bias in the unsupported ones. For metallic tubes we observed that interference patterns of electron waves caused by defects and edges are more pronounced on suspended nanotubes than the supported nanotubes. Interestingly, the pattern do not decay on suspended nanotubes indicating that the coherence length is much longer than what was reported earlier on supported nanotubes. These results highlight the role of substrate–nanotubes interactions and shed some light on their influences on nanotube devices.