Photoconductivity in defective carbon nanotube sheets under ultraviolet-visible-near infrared radiation

Multiwalled carbon nanotube sheets of relatively large area have been grown on a sapphire substrate by chemical vapor deposition at the substrate temperature of 500 and 750 degrees C. The photoconductivity measurements, performed under white light and monochromatic radiation in the ultraviolet-visible-near infrared region, show that the highly defective sample grown at 500 degrees C has a higher photosensitivity, thus revealing the crucial role of structural defects in determining the overall photoresponse of the nanotube's sheets. The spectral photoresponse of these nanostructured films increases with the increase in photon energy, and is strongly correlated to the absorbance. The photoconductivity properties of these materials are favorable in potential development of large area light sensors as well as optoelectronic nanodevices.