Imaging electron wave functions of quantized energy levels in carbon nanotubes

Carbon nanotubes provide a unique system for studying one-dimensional quant ization phenomena. Scanning tunneling microscopy was used to observe the el ectronic wave functions that correspond to quantized energy Levels in short metallic carbon nanotubes. Discrete electron waves were apparent from peri odic oscillations in the differential conductance as a function of the posi tion along the tube axis, with a period that differed from that of the atom ic Lattice. Wave functions could be observed for several electron states at adjacent discrete energies. The measured wavelengths are in good agreement with the calculated Fermi wavelength for armchair nanotubes.