Photo-induced tunneling current in single-wall carbon nanotubes investigated by scanning tunneling spectroscopy

The electronic properties of single-wall carbon nanotubes (SWCNT) under light excitation were investigated by scanning tunneling microscopy and spectroscopy (STM/STS), since this technique allows both imaging and probing individual nanotubes. A photo-induced tunneling current (PITC) was observed for semiconducting and metallic SWNT only when the excitation energy exceeds the 1(st) pairs of van Hove singularity in the density of state. Moreover, the PrrC effect occurs at both positive and negative sample bias, increases linearly with the light intensity and is reversible. Further experiments are in progress to elucidate the mechanism of PITC and to ultimately reveal the photoconductivity response of individual SWCNT.