Photoconductivity of single-walled carbon nanotubes under CW illumination

The photoconductive response of single-walled carbon nanotubes (SWNTs) has been studied under CW illumination in the NIR (900-1800 nm) and far-IR (9-10 /spl mu/m) range. SWNTs were coated onto patterned gold electrodes with spacing which was varied from 5 to 300 nm. SWNT samples exhibit absorption NIR bands that are typical for semiconducting nanotubes with a diameter distribution of 0.8-1.1 nm and band at /spl sim/10 /spl mu/m in the far-IR range. A clear correlation between current and IR exposure has been observed. The detection of photoconductivity requires instrumentation with a high dynamic range due to a significant dark current. The photocurrent exhibits a linear response with light intensity and with bias voltage. Possible mechanisms of photoconductivity in SWNT films and applications of this new photosensitive material are discussed.