Photoconductivity of single-walled carbon nanotubes

We have investigated photoconducting properties of mat samples of single-walled carbon nanotubes (SWNTs) in order to clarify the mechanism of photoconductivity. Two peaks are observed in photoconductivity spectra around 0.7 and 1.2 eV for both samples of SWNTs synthesized by arc discharge and laser ablation methods, which can be interpreted as the photocurrent in the semiconductor phase of nanotubes. No threshold in applied voltage is observed for the occurrence of photoconductivity. Results show that the photoconductivity is an intrinsic feature of SWNTs and that junction areas do not play an important role on photoconductivity.