SCANNING-TUNNELING-MICROSCOPY AND SPECTROSCOPY STUDIES OF SINGLE WALLCARBON NANOTUBES

Scanning tunneling microscopy and spectroscopy have been used to chara cterize the atomic structure and tunneling density of states of indivi dual single wall carbon nanotubes (SWNT's) and ropes containing many S WNT's. Analysis of atomically resolved SWNT images shows that the nano tubes consist of a wide range of diameters and helicities with no one structure clearly dominant. Tunneling spectroscopy measurements made s imultaneously on atomically resolved SWNT's exhibit semiconducting and metallic behavior that depend predictably on helicity and diameter. I n addition the band gaps of the semiconducting tubes were also found t o depend inversely on diameter. These results are compared to theoreti cal predictions, and the implications of these studies as well as impo rtant future directions are discussed.