Photoconductivity of single-wall carbon nanotube films

Time-resolved photoconductivity measurements were carried Out on single-wall carbon nanotube (SWNT) films at various temperatures. Photoconductivity excitation spectra show two clear peaks around 0.7 and 1.2 eV. Observed peaks in the spectra correspond to the optical absorption between symmetrical bands of semiconducting SWNTs. The analysis of this feature allows insight into the transport properties of semiconducting SWNTs. Signal profiles in the photoresponse at low temperatures depend strongly on the sample, while intensity of the photoresponse monotonously increases with a decrease in temperature for all samples. Photo-induced current for a sample decays rapidly after the laser pulse irradiation. For another sample, on the other hand, it decreases gradually and remains up to a few hundred nanoseconds, showing the existence of trapping sites in the nanotubes. (C) 2004 Elsevier Ltd. All rights reserved.